CN112839502B - Electromagnetic shielding layer - Google Patents
Electromagnetic shielding layer Download PDFInfo
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- CN112839502B CN112839502B CN202110167796.XA CN202110167796A CN112839502B CN 112839502 B CN112839502 B CN 112839502B CN 202110167796 A CN202110167796 A CN 202110167796A CN 112839502 B CN112839502 B CN 112839502B
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K9/00—Screening of apparatus or components against electric or magnetic fields
- H05K9/0073—Shielding materials
- H05K9/0081—Electromagnetic shielding materials, e.g. EMI, RFI shielding
- H05K9/0088—Electromagnetic shielding materials, e.g. EMI, RFI shielding comprising a plurality of shielding layers; combining different shielding material structure
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K9/00—Screening of apparatus or components against electric or magnetic fields
- H05K9/0073—Shielding materials
- H05K9/0081—Electromagnetic shielding materials, e.g. EMI, RFI shielding
- H05K9/0086—Electromagnetic shielding materials, e.g. EMI, RFI shielding comprising a single discontinuous metallic layer on an electrically insulating supporting structure, e.g. metal grid, perforated metal foil, film, aggregated flakes, sintering
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K9/00—Screening of apparatus or components against electric or magnetic fields
- H05K9/0073—Shielding materials
- H05K9/0081—Electromagnetic shielding materials, e.g. EMI, RFI shielding
- H05K9/009—Electromagnetic shielding materials, e.g. EMI, RFI shielding comprising electro-conductive fibres, e.g. metal fibres, carbon fibres, metallised textile fibres, electro-conductive mesh, woven, non-woven mat, fleece, cross-linked
Abstract
The invention belongs to the technical field of electromagnetic shielding, and particularly relates to an electromagnetic shielding layer. An electromagnetic shielding layer sequentially comprises a first fluorine-containing polyimide protective layer, a first silver nanowire layer, a fluorine-containing polyimide substrate, a second silver nanowire layer and a second fluorine-containing polyimide protective layer from top to bottom; the fluorine-containing polyimide substrate, the first fluorine-containing polyimide protective layer and the second fluorine-containing polyimide protective layer are prepared by coating fluorine-containing polyimide glue solution; the first silver nanowire layer and the second silver nanowire layer are prepared by coating silver nanowire coating liquid. The electromagnetic shielding layer adopts the electromagnetic shielding film compounded by fluorine-containing polyimide and the silver nanowires, and the electromagnetic shielding layer which is light, long in service life and capable of being curled is obtained by utilizing the characteristics of high mechanical property, high temperature resistance, light weight and high transmittance of the silver nanowires.
Description
Technical Field
The invention belongs to the technical field of electromagnetic shielding, and particularly relates to an electromagnetic shielding layer.
Background
With the rapid development of electronic technology, people can communicate, exchange and surf the internet by utilizing the electromagnetic technology, and the electromagnetic technology provides great convenience for human life. However, with the development of electromagnetic shielding technology, the electromagnetic shielding technology also brings adverse factors to people, and electromagnetic interference not only affects the normal work of the electronic society, but also may threaten the physical health of people. Therefore, the function of the electromagnetic shielding material is becoming more important, the electromagnetic shielding material in the prior art is made of metal material, and the electromagnetic shielding material made of metal material has the problems of heavy weight, easy corrosion, large processing difficulty and the like. It is seen that there is a need in the art for a new electromagnetic shielding material to solve the above problems.
Disclosure of Invention
In order to solve the problems, the invention provides a preparation method of an electromagnetic shielding layer compounded by fluorine-containing polyimide and silver nanowires. The electromagnetic shielding layer provided by the invention is light in weight, corrosion-resistant and easy to process. The invention adopts the following technical scheme.
An electromagnetic shielding layer sequentially comprises a first fluorine-containing polyimide protective layer, a first silver nanowire layer, a fluorine-containing polyimide substrate, a second silver nanowire layer and a second fluorine-containing polyimide protective layer from top to bottom; the fluorine-containing polyimide substrate, the first fluorine-containing polyimide protective layer and the second fluorine-containing polyimide protective layer are prepared by coating fluorine-containing polyimide glue solution; the first silver nanowire layer and the second silver nanowire layer are prepared by coating silver nanowire coating liquid.
Further, the fluorine-containing polyimide glue solution is prepared by the following method:
(1) dissolving 6FDA (4,4' - (hexafluoroisopropylidene) diphthalic anhydride) and PFMB (2,2' -bis-trifluoromethyl-4, 4' -diaminobiphenyl) in a stirred solution of m-cresol containing isoquinoline under an inert atmosphere, continuously stirring for more than 3 hours, and then heating and refluxing the solution to obtain a mixture A;
(2) after the mixture A is cooled to room temperature, diluting the mixture A by adopting m-cresol, and then adding the mixture A into a stirring ethanol solution with the volume fraction of 95% to obtain a mixture B;
(3) filtering the mixture B, collecting precipitate, and cleaning and drying the precipitate to obtain a mixture C;
(4) and dissolving the mixture C in gamma-butyrolactone to obtain the fluorine-containing polyimide solution.
The fluorine-containing polyimide glue solution is adopted, so that the phenomenon that a film material is in a yellow brown color or other dark colors due to the conjugation of chromophoric group electron clouds in molecules in a polyimide film layer in the prior art is avoided. In the fluorine-containing polyimide of the present invention, fluorine atoms are introduced into a polyimide molecular chain, so that electron cloud conjugation of a chromophoric group in the polyimide can be destroyed, but the rigid structure of the polyimide is not destroyed. Therefore, the fluorine-containing polyimide glue solution adopted in the invention keeps better optical performance besides the bending resistance and high temperature resistance of the original polyimide material, and improves the dielectric property of the polyimide material.
Further, the fluorine-containing polyimide solution has a solid content of 8 wt.% to 12 wt.%.
Further, the silver nanowire coating liquid comprises the following raw materials in parts by mass: 0.01-1 part of silver nanowires, 0.01-5 parts of dispersing resin, 0.002-1 part of flux, 0.001-0.2 part of wetting agent and 82.26-90.911 parts of solvent.
Further, the dispersion resin includes polyacrylic acid series.
Further, the polyacrylic acid-based substance is any one of polymethacrylate, polyvinyl alcohol, Polyurethane (PU), polycarbonate, epoxy resin, cellulose, polysaccharide, and starch.
Further, the flux is a reducing organic amine or acid or a reducing organic amine salt.
Further, the reducing organic amine includes primary amine, secondary amine, and tertiary amine or a N-containing heterocyclic compound.
Further, the N heterocyclic compound is one of ethylenediamine, diethylamine, aniline, diethanolamine, triethanolamine, hydrazines, guanidines, pyridine and quinoline.
Further, the acid is one or more of organic acid or inorganic acid.
Further, the organic acid includes one of formic acid, acetic acid, maleic acid, oxalic acid, succinic acid, adipic acid, succinic anhydride (succinic anhydride), NA anhydride, dibromsuccinic acid, sebacic acid, glutaric acid, itaconic acid, salicylic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid (palmitic acid), octadecanoic acid, stearic acid, palmitic acid, tartaric acid, DL-malic acid, sorbic acid, phthalic acid, benzoic acid, p-tert-butylbenzoic acid, chloroglycolic acid, glycolic acid, maleic anhydride (maleic anhydride), maleic acid, lactic acid, malonic acid, azelaic acid, suberic acid, dodecanedioic acid, dimethylolpropionic acid, polymeric acid, oleic acid, citric acid.
Further, the inorganic acid includes one of hydrochloric acid, nitric acid, hydrobromic acid, sulfurous acid, thiosulfuric acid, fluoroboric acid, and phosphorous acid.
Further, the wetting agent is a fluorine surfactant or a nonionic surfactant of alkylphenol ethoxylates.
Furthermore, the solvent is one or more of ketone, ester, ether and alcohol.
Further, the solvent is one or more of ethanol, isopropanol, acetone and methyl ethyl ether.
Further, the concentration of the silver nanowire coating liquid is 0.01 wt.% to 1.0 wt.%.
Furthermore, the length of the silver nanowire in the silver nanowire coating liquid is 30-100 micrometers, and the diameter of the silver nanowire coating liquid is 8-30 nm.
The silver nanowire is a main component for endowing the electromagnetic shielding layer with shielding performance, and the resistance of the silver nanowire is a main index for exerting the electromagnetic shielding performance of the silver nanowire. The resistance of the silver nanowires is mainly determined by the resistance value of a single silver nanowire, the number of the silver nanowires, the number of connections between the silver nanowires and the contact resistance. The resistance of a single silver nanowire is mainly limited by the length and the direction of the silver nanowire, and the number of the silver nanowires, the number of connections between the silver nanowires and the contact resistance are mainly determined by the solubility and the components of the silver nanowire coating liquid. According to the invention, the brazing flux is added into the silver nanowire coating liquid, so that the silver nanowire contact points can be better fused, and the contact resistance is effectively reduced. The concentration of the silver nanowires and the size of the silver nanowires are limited, so that the problem that the silver nanowires are not isolated too far when the concentration of the silver nanowires is low, and a continuous current path is not provided, so that the resistance is high is avoided, and the problems that the haze of a silver nanowire layer is increased due to light scattering of the silver nanowires when the concentration of the silver nanowires is high are also avoided.
Compared with the prior art, the invention achieves the following beneficial effects.
The electromagnetic shielding layer is compounded by the fluorine-containing polyimide and the silver nanowires, so that the electromagnetic shielding layer is good in electromagnetic shielding performance and has shielding benefits for electromagnetic waves in a non-frequency band. The invention utilizes the characteristics of high mechanical property, high temperature resistance, light weight and high transmittance of the fluorine-containing polyimide layer and the silver nanowire to obtain the electromagnetic shielding layer which is light in weight, long in service life and capable of being curled.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a cross-sectional view of an electromagnetic shield in one embodiment of the present invention;
FIG. 2 is a schematic structural view of a bezel, a through hole, and a clip according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of an electromagnetic shielding chamber according to an embodiment of the present invention;
the structure comprises a substrate, a first fluorine-containing polyimide protective layer, a second silver nanowire layer, a 3-fluorine-containing polyimide substrate, a 4-second silver nanowire layer, a 5-second fluorine-containing polyimide protective layer, a 6-frame, a 61-through hole and a 62-buckle.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
An electromagnetic shielding layer is prepared by the following method:
(1) coating the fluorine-containing polyimide solution on a PET (polyethylene terephthalate) base material by adopting a slit coating mode, forming a film by three sections of temperature control ovens at 60 ℃, 120 ℃ and 150 ℃, and manually stripping the film to obtain a fluorine-containing polyimide substrate;
(2) coating the silver nanowire coating liquid on the upper surface of the fluorine-containing polyimide substrate by adopting a wet coating mode to form a first silver nanowire layer, and coating the silver nanowire coating liquid on the lower surface of the fluorine-containing polyimide substrate by adopting a wet coating mode to form a second silver nanowire layer;
(3) and coating the fluorine-containing polyimide solution on the first silver nanowire layer by adopting a slit coating mode to form a first fluorine-containing polyimide protective layer, and coating the fluorine-containing polyimide solution on the lower surface of the second silver nanowire layer by adopting a slit coating mode to form a second fluorine-containing polyimide protective layer, thus obtaining the electromagnetic shielding layer.
The fluorine-containing polyimide glue solution is prepared by the following method:
(1) 1.5mol of 6FDA (4,4' - (hexafluoroisopropylidene) diphthalic anhydride) and 1.5mol of PFMB (2,2' -bistrifluoromethyl-4, 4' -diaminobiphenyl) were dissolved in a stirred solution of 100g of isoquinoline in 1.5L of m-cresol at ambient temperature under a nitrogen atmosphere and stirring was continued for 3 hours, and then the solution was heated to 80 ℃ and refluxed for 3 hours to give a mixture A;
(2) after the mixture A is cooled to room temperature, 20L of m-cresol is adopted to dilute the mixture A, and then the mixture A is added into an ethanol solution with the volume fraction of 95% in a stirring state to obtain a mixture B;
(3) filtering the mixture B, collecting precipitate, washing the precipitate with ethanol, and drying at 150 deg.C under reduced pressure for 24 hr to obtain mixture C;
(4) and dissolving the mixture C in gamma-butyrolactone to obtain a fluorine-containing polyimide solution, wherein the solid content of the fluorine-containing polyimide is controlled to be 10%.
The silver nanowire coating liquid comprises the following raw materials in parts by mass: 0.75g of silver nanowires, 3g of polymethacrylate, 0.5g of primary amine, 0.2g of fluorinated surfactant and 85g of ethanol.
The concentration of the silver nanowire coating liquid was 0.8 wt.%.
The silver nanowires in the silver nanowire coating liquid had a length of 60 μm and a diameter of 20 nm.
As shown in fig. 1 to 3, the prepared electromagnetic shielding layer is cut into a rectangular parallelepiped electromagnetic shielding layer with a length and a width of 100mm, the electromagnetic shielding layer sequentially comprises a first fluorine-containing polyimide protective layer 1, a first silver nanowire layer 2, a fluorine-containing polyimide substrate 3, a second silver nanowire layer 4 and a second fluorine-containing polyimide protective layer 5 from top to bottom, the first fluorine-containing polyimide protective layer 1 has a thickness of 10 μm, the first silver nanowire layer 2 has a thickness of 30nm, the fluorine-containing polyimide substrate 3 has a thickness of 125 μm, the second silver nanowire layer 4 has a thickness of 30nm, and the second fluorine-containing polyimide protective layer 5 has a thickness of 10 μm. The edges of the upper surface of the first fluorine-containing polyimide protective layer 1 and the lower surface of the second fluorine-containing polyimide protective layer 5 are subjected to plasma pretreatment, lead chloride allelochemicals are used, and then copper metal film frames 6 are formed by chemical plating through copper sulfate electroplating liquid. In the manufacturing process of the copper metal film, the first polyimide protective layer 1 and the second polyimide protective layer 5 are damaged, so that the metal film is in contact with the first silver nanowire layer 2 and the second silver nanowire layer 4, and the electric conduction is realized. Be provided with through-hole 61 and buckle 62 on the frame 6, buckle 62 one end is connected with through-hole 61 on the frame 6 welding other end and the other electromagnetic shielding layer, can form a square electromagnetic shielding cavity that length width height is 100mm with rectangular electromagnetic shielding layer like this. Specifically, the latch 62 is a metal latch, so that the electromagnetic shielding chamber forms a closed conductive loop.
Example 2
An electromagnetic shielding layer is prepared by the following method:
(1) coating the fluorine-containing polyimide solution on a PET (polyethylene terephthalate) base material in a slit coating mode, forming a film through a three-section temperature control oven at 60 ℃, 120 ℃ and 150 ℃, and manually stripping the film to obtain a fluorine-containing polyimide substrate;
(2) coating the silver nanowire coating liquid on the upper surface of the fluorine-containing polyimide substrate by adopting a wet coating mode to form a first silver nanowire layer, and coating the silver nanowire coating liquid on the lower surface of the fluorine-containing polyimide substrate by adopting a wet coating mode to form a second silver nanowire layer;
(3) and coating the fluorine-containing polyimide solution on the first silver nanowire layer by adopting a slit coating mode to form a first fluorine-containing polyimide protective layer, and coating the fluorine-containing polyimide solution on the lower surface of the second silver nanowire layer by adopting a slit coating mode to form a second fluorine-containing polyimide protective layer, so as to obtain the electromagnetic shielding layer.
The fluorine-containing polyimide glue solution is prepared by the following method:
(1) 1.5mol of 6FDA (4,4' - (hexafluoroisopropylidene) diphthalic anhydride) and 1.5mol of PFMB (2,2' -bistrifluoromethyl-4, 4' -diaminobiphenyl) were dissolved in a stirred solution of 100g of isoquinoline in 1.5L of m-cresol at ambient temperature under a nitrogen atmosphere and stirred continuously for 3 hours, and then the solution was heated to 80 ℃ and refluxed for 3 hours to obtain a mixture A;
(2) after the mixture A is cooled to room temperature, 20L of m-cresol is adopted to dilute the mixture A, and then the mixture A is added into an ethanol solution with the volume fraction of 95% in a stirring state to obtain a mixture B;
(3) filtering the mixture B, collecting precipitate, washing the precipitate with ethanol, and drying at 150 deg.C under reduced pressure for 24 hr to obtain mixture C;
(4) and dissolving the mixture C in gamma-butyrolactone to obtain a fluorine-containing polyimide solution, wherein the solid content of the fluorine-containing polyimide is controlled to be 10%.
The silver nanowire coating liquid comprises the following raw materials in parts by mass: 0.01g of silver nanowire, 0.02g of polymethacrylate, 0.01g of hydrochloric acid, 0.1g of fluorinated surfactant and 83g of ethanol.
The concentration of the silver nanowire coating liquid was 0.01 wt.%.
The silver nanowires in the silver nanowire coating liquid had a length of 30 μm and a diameter of 10 nm.
As shown in fig. 1 to 3, the prepared electromagnetic shielding layer is cut into a rectangular parallelepiped electromagnetic shielding layer with a length and a width of 100mm, the electromagnetic shielding layer sequentially comprises a first fluorine-containing polyimide protective layer 1, a first silver nanowire layer 2, a fluorine-containing polyimide substrate 3, a second silver nanowire layer 4 and a second fluorine-containing polyimide protective layer 5 from top to bottom, the first fluorine-containing polyimide protective layer 1 has a thickness of 9 μm, the first silver nanowire layer 2 has a thickness of 28nm, the fluorine-containing polyimide substrate 3 has a thickness of 120 μm, the second silver nanowire layer 4 has a thickness of 32nm, and the second fluorine-containing polyimide protective layer 5 has a thickness of 9 μm. The edges of the upper surface of the first fluorine-containing polyimide protective layer 1 and the lower surface of the second fluorine-containing polyimide protective layer 5 are subjected to plasma pretreatment, lead chloride is used for sensitization, and then copper metal film frames 6 are formed by chemical plating through copper sulfate electroplating solution. In the manufacturing process of the copper metal film, the first polyimide protective layer 1 and the second polyimide protective layer 5 are damaged, so that the metal film is in contact with the first silver nanowire layer 2 and the second silver nanowire layer 4, and the electric conduction is realized. The frame 6 is provided with a through hole 61 and a buckle 62, one end of the buckle 62 is connected with the through hole 61 on the other electromagnetic shielding layer by welding the frame 6, so that the rectangular electromagnetic shielding layers can form a square electromagnetic shielding chamber with the length, width and height of 100 mm. In particular, the latch 62 is a metal latch, so that the electromagnetic shielding chamber forms a closed conductive loop.
Example 3
An electromagnetic shielding layer is prepared by the following method:
(1) coating the fluorine-containing polyimide solution on a PET (polyethylene terephthalate) base material in a slit coating mode, forming a film through a three-section temperature control oven at 60 ℃, 120 ℃ and 150 ℃, and manually stripping the film to obtain a fluorine-containing polyimide substrate;
(2) coating the silver nanowire coating liquid on the upper surface of the fluorine-containing polyimide substrate by adopting a wet coating mode to form a first silver nanowire layer, and coating the silver nanowire coating liquid on the lower surface of the fluorine-containing polyimide substrate by adopting a wet coating mode to form a second silver nanowire layer;
(3) and coating the fluorine-containing polyimide solution on the first silver nanowire layer by adopting a slit coating mode to form a first fluorine-containing polyimide protective layer, and coating the fluorine-containing polyimide solution on the lower surface of the second silver nanowire layer by adopting a slit coating mode to form a second fluorine-containing polyimide protective layer, thus obtaining the electromagnetic shielding layer.
The fluorine-containing polyimide glue solution is prepared by the following method:
(1) 1.5mol of 6FDA (4,4' - (hexafluoroisopropylidene) diphthalic anhydride) and 1.5mol of PFMB (2,2' -bistrifluoromethyl-4, 4' -diaminobiphenyl) were dissolved in a stirred solution of 100g of isoquinoline in 1.5L of m-cresol at ambient temperature under a nitrogen atmosphere and stirring was continued for 3 hours, and then the solution was heated to 80 ℃ and refluxed for 3 hours to give a mixture A;
(2) after the mixture A is cooled to room temperature, 20L of m-cresol is adopted to dilute the mixture A, and then the mixture A is added into an ethanol solution with the volume fraction of 95% in a stirring state to obtain a mixture B;
(3) filtering the mixture B, collecting precipitate, washing the precipitate with ethanol, and drying at 150 deg.C under reduced pressure for 24 hr to obtain mixture C;
(4) and dissolving the mixture C in gamma-butyrolactone to obtain a fluorine-containing polyimide solution, wherein the solid content of the fluorine-containing polyimide is controlled to be 10%.
The silver nanowire coating liquid comprises the following raw materials in parts by mass: 0.5g of silver nanowires, 3g of polymethacrylate, 0.8g of acetic acid, 0.15g of fluorinated surfactant and 90g of ethanol.
The concentration of the silver nanowire coating liquid was 0.5 wt.%.
The silver nanowires in the silver nanowire coating liquid had a length of 90 μm and a diameter of 25 nm.
As shown in fig. 1 to 3, the prepared electromagnetic shielding layer is cut into a rectangular parallelepiped electromagnetic shielding layer with a length and a width of 100mm, the electromagnetic shielding layer sequentially comprises a first fluorine-containing polyimide protective layer 1, a first silver nanowire layer 2, a fluorine-containing polyimide substrate 3, a second silver nanowire layer 4 and a second fluorine-containing polyimide protective layer 5 from top to bottom, the first fluorine-containing polyimide protective layer 1 has a thickness of 11 μm, the first silver nanowire layer 2 has a thickness of 32nm, the fluorine-containing polyimide substrate 3 has a thickness of 130 μm, the second silver nanowire layer 4 has a thickness of 28nm, and the second fluorine-containing polyimide protective layer 5 has a thickness of 11 μm. The edges of the upper surface of the first fluorine-containing polyimide protective layer 1 and the lower surface of the second fluorine-containing polyimide protective layer 5 are subjected to plasma pretreatment, lead chloride is used for sensitization, and then copper metal film frames 6 are formed by chemical plating through copper sulfate electroplating solution. In the manufacturing process of the copper metal film, the first polyimide protective layer 1 and the second polyimide protective layer 5 are damaged, so that the metal film is in contact with the first silver nanowire layer 2 and the second silver nanowire layer 4, and the electric conduction is realized. Be provided with through-hole 61 and buckle 62 on the frame 6, buckle 62 one end is connected with through-hole 61 on the frame 6 welding other end and the other electromagnetic shielding layer, can form a square electromagnetic shielding cavity that length width height is 100mm with rectangular electromagnetic shielding layer like this. In particular, the latch 62 is a metal latch, so that the electromagnetic shielding chamber forms a closed conductive loop.
Comparative example 1
Comparative example 1 was prepared on the basis of example 1, and comparative example 1 is different from example 1 in that the fluorine-containing polyimide was replaced with SMW type polyimide manufactured by chang. The remaining features are the same as in example 1.
Comparative example 2
Comparative example 2 was set on the basis of example 1, and the technical feature of comparative example 2, which is different from example 1, is that the silver nanowire coating liquid includes the following raw materials by mass: 1.5g of silver nanowires, 3g of polymethacrylate, 0.8g of primary amine, 0.15g of fluorinated surfactant and 92g of ethanol. The solubility of the silver nanowire coating liquid was 1.5 wt.%. The remaining features are the same as in example 1.
Comparative example 3
Comparative example 3 was set on the basis of example 1, and the technical feature of comparative example 3, which is different from example 1, is that the silver nanowire coating liquid includes the following raw materials by mass: 0.001g of silver nanowires, 3g of polymethacrylate, 0.8g of primary amine, 0.15g of fluorinated surfactant and 92g of ethanol. The solubility of the silver nanowire coating liquid was 0.001 wt.%. The remaining features are the same as in example 1.
The shielding performance of the electromagnetic shielding chambers prepared in examples 1-3 and comparative examples 1-3 was tested according to the national standard GJB 6190 and 2008 method for measuring shielding effectiveness of electromagnetic shielding material. The test results are shown in table 1.
TABLE 1 test results of electromagnetic shielding properties
The electromagnetic shielding chambers prepared in examples 1 to 3 and comparative examples 1 to 3 were placed in a salt spray machine for salt spray testing, and the stability of the apparatus was tested. The test results are shown in table 2.
Table 2 salt spray test results for electromagnetic shielding chamber
The electromagnetic shielding chamber prepared by the embodiment is placed into a cold and hot impact testing machine, and the cold and hot circulation high and low temperature test and the stability of the device are carried out on the electromagnetic shielding chamber. The test results are shown in table 3.
Table 3 stability test results of electromagnetic shielding chamber
In conclusion, the electromagnetic shielding cavity prepared by the invention has excellent electromagnetic shielding performance and has shielding performance on electromagnetic waves of different frequency bands. Meanwhile, the electromagnetic shielding chamber prepared by the invention has good corrosion resistance, and the spraying pressure is 1kg/cm when the salt water is 5 wt.% 2 When the laboratory temperature is 35 ℃, the saturation barrel temperature is 47 ℃ and the time is 240 hours, the light transmittance, the haze and the sheet resistance of the electromagnetic shielding chamber do not change obviouslyAnd (4) transforming. In addition, the electromagnetic shielding cavity prepared by the invention has good stability, and in a cold and hot impact testing machine, the light transmittance is 86-88% at the low temperature of-20 ℃ and the high temperature of 60 ℃, the haze is 1.3-1.6%, and the sheet resistance is 10-12 omega. Comparative example 1 is an electromagnetic shielding chamber prepared using polyimide containing no fluorine, the prepared electromagnetic shielding chamber has a high haze of 2.03 in the absence of external conditions, and the haze increases significantly during salt spray testing and high and low temperature testing. The concentration of the silver nanowires coated in comparative example 2 was large, and the haze of the prepared electromagnetic shielding layer was 8.07, which was high. The silver nanowire coated in comparative example 3 has a low concentration, and the electromagnetic shielding layer prepared therefrom has a high sheet resistance and poor electromagnetic shielding performance.
The present invention has been further described with reference to specific embodiments, but it should be understood that the specific description herein should not be construed as limiting the spirit and scope of the invention, and that various modifications to the above-described embodiments, which would occur to persons skilled in the art upon reading this description, are within the scope of the invention.
Claims (8)
1. The electromagnetic shielding layer is characterized by sequentially comprising a first fluorine-containing polyimide protective layer, a first silver nanowire layer, a fluorine-containing polyimide substrate, a second silver nanowire layer and a second fluorine-containing polyimide protective layer from top to bottom; the fluorine-containing polyimide substrate, the first fluorine-containing polyimide protective layer and the second fluorine-containing polyimide protective layer are prepared by coating fluorine-containing polyimide glue solution; the first silver nanowire layer and the second silver nanowire layer are prepared by coating silver nanowire coating liquid;
the concentration of the silver nanowires in the silver nanowire coating liquid is 0.01-1.0 wt.%;
the length of the silver nanowire in the silver nanowire coating liquid is 30-100 micrometers, and the diameter of the silver nanowire coating liquid is 8-30 nm;
the thickness of the first fluorine-containing polyimide protective layer is 10 micrometers, the thickness of the first silver nanowire layer is 30nm, the thickness of the fluorine-containing polyimide substrate is 125 micrometers, the thickness of the second silver nanowire layer is 30nm, and the thickness of the second fluorine-containing polyimide protective layer is 10 micrometers; or
The thickness of the first fluorine-containing polyimide protective layer is 9 micrometers, the thickness of the first silver nanowire layer is 28nm, the thickness of the fluorine-containing polyimide substrate is 120 micrometers, the thickness of the second silver nanowire layer is 32nm, and the thickness of the second fluorine-containing polyimide protective layer is 9 micrometers; or
The thickness of the first fluorine-containing polyimide protective layer was 11 μm, the thickness of the first silver nanowire layer was 32nm, the thickness of the fluorine-containing polyimide substrate was 130 μm, the thickness of the second silver nanowire layer was 28nm, and the thickness of the second fluorine-containing polyimide protective layer was 11 μm.
2. The electromagnetic shielding layer according to claim 1, wherein the fluorine-containing polyimide glue solution is prepared by the following method:
(1) dissolving 4,4' - (hexafluoroisopropylidene) diphthalic anhydride and 2,2' -bis (trifluoromethyl) -4,4' -diaminobiphenyl in a stirred solution of isoquinoline-containing m-cresol under inert atmosphere, continuously stirring for more than 3 hours, and then heating and refluxing the solution to obtain a mixture A;
(2) after the mixture A is cooled to room temperature, diluting the mixture A by adopting m-cresol, and then adding the mixture A into a stirring ethanol solution with the volume fraction of 95% to obtain a mixture B;
(3) filtering the mixture B, collecting precipitate, and cleaning and drying the precipitate to obtain a mixture C;
(4) and dissolving the mixture C in gamma-butyrolactone to obtain the fluorine-containing polyimide solution.
3. The electromagnetic shielding layer of claim 2, wherein the fluorine-containing polyimide glue solution has a solid content of 8 wt.% to 12 wt.%.
4. The electromagnetic shielding layer of claim 1, wherein the silver nanowire coating solution comprises the following raw materials in parts by mass: 0.01-1 part of silver nanowires, 0.01-5 parts of dispersion resin, 0.002-1 part of flux, 0.001-0.2 part of wetting agent and 82.26-90.911 parts of solvent.
5. The electromagnetic shielding layer of claim 4 wherein the dispersing resin comprises a polyacrylic.
6. Electromagnetic shielding layer according to claim 4, characterized in that the flux agent is a reducing organic amine or an acid or a salt of a reducing organic amine.
7. The electromagnetic shielding layer according to claim 4, wherein the wetting agent is a fluorosurfactant or a nonionic surfactant of alkylphenol ethoxylates.
8. The electromagnetic shielding layer of claim 4, wherein the solvent is one or more of ketone, ester, ether, and alcohol.
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