Patent Application
20110291032
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1. Field of the Invention
The disclosure relates to an electromagnetic shielding composition, and particularly relates to an electromagnetic shielding composition including nanowires and nanoparticles.
2. Description of Related Art
Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
With the advancement of wireless technology, wireless communication devices such as mobile phones are widely used. Because wireless communication devices and base stations all may emit electromagnetic radiation, electromagnetic pollution fills our living environment. In addition, electronic products used in our daily life, such as computers or microwave ovens, may also emit weak electromagnetic energy.
According to a report released in 1998 by the World Health Organization, people who experience long-term exposure to electromagnetic radiation above safe levels are more likely to suffer from cardiovascular diseases, diabetes or cancer. Long-term exposure to high electromagnetic radiation level may cause disorders of reproductive, immune, or nervous systems, or cause miscarriage, deformed fetuses or sterility. Children exposed to electromagnetic radiation at high levels for a long period may suffer from abnormally slow bone growth, deterioration of hematopoietic function, and suffer from vision deterioration and retinal detachment. Thus, electromagnetic radiation seriously affects human health.
One conventional method to shield electromagnetic radiation is to use a metal piece or a metal shell. However, because metal is heavy, not easily formed into a desired shape, and is prone to oxidation during long-term use, metal is not suitable for use in many types of electronic devices.
Another method for shielding electromagnetic radiation is to form an electromagnetic shielding layer on a body using a mixture of metal particles and an adhesive or lacquer. The electromagnetic shielding layer is light-weight, and is not limited to the shape of a target. However, to obtain a desirable electromagnetic shielding effectiveness, high concentration of metal particles in the mixture is needed. Although a high concentration level of metal particles may enable better electromagnetic shielding effectiveness, the plasticity and the strength of the mixture may be lowered, and the advantages of the mixture such as ease of manufacturing, light weight, and low cost are lost. In addition, the electromagnetic shielding layer usually includes metal particles with a single shape. To improve the electromagnetic shielding performance by increasing the amount of metal particles with such a single shape does not significantly improve the electromagnetic shielding effectiveness.
In addition, conventional electromagnetic shielding layers need a thickness of 250 micrometers so as to have sufficient electromagnetic shielding effect. However, a thick electromagnetic shielding layer has poor uniformity and consumes more material.
In consideration of the deficiencies of conventional methods for shielding electromagnetic radiation, an electromagnetic shielding material having advantages such as high electromagnetic shielding effectiveness, low cost, and ease of use is required.
One embodiment of the present disclosure provides an electromagnetic shielding composition, which comprises a carrier, a plurality of metal nanowires, and a plurality of nanoparticles. The plurality of metal nanowires are dispersed within the carrier, wherein based upon the total weight of the composition taken as 100 percent, the metal nanowires are in an amount of between 1 and 95 percent by weight of the electromagnetic shielding composition. The plurality of nanoparticles are dispersed within the carrier, wherein based upon the total weight of the composition taken as 100 percent, the nanoparticles are in an amount of between 0.1 and 60 percent by weight of the electromagnetic shielding composition.
In another embodiment, an electromagnetic shielding composition is provided. The electromagnetic shielding composition comprises a carrier, a plurality of metal nanowires, and a plurality of nanoparticles. The plurality of metal nanowires are dispersed within the carrier. The plurality of metal nanowires have an aspect ratio of greater than 10. The metal nanowires comprise gold, silver, copper, indium, palladium, aluminum, iron, cobalt, nickel, an oxide thereof, or a mixture thereof, wherein the plurality of metal nanowires are in an amount of from 1 to 95 percent based upon the total weight of the electromagnetic shielding composition taken as 100 percent by weight. The plurality of nanoparticles are dispersed within the carrier. The nanoparticles have a size of less than 1000 nanometers. The nanoparticles comprise gold, silver, copper, indium, palladium, aluminum, iron, cobalt, nickel, an alloy thereof, an oxide thereof, or a mixture thereof, wherein the plurality of nanoparticles are in an amount of from 0.1 to 60 percent based upon the total weight of the electromagnetic shielding composition taken as 100 percent by weight.
In another embodiment, an electromagnetic shielding composition is provided. The electromagnetic shielding composition comprises a carrier, a plurality of metal nanowires, and a plurality of nanoparticles. The plurality of metal nanowires are dispersed within the carrier. The plurality of metal nanowires have an aspect ratio of greater than 10. The metal nanowires comprise gold, silver, copper, indium, palladium, aluminum, iron, cobalt, nickel, an oxide thereof, or a mixture thereof. The plurality of nanoparticles are dispersed within the carrier. The nanoparticles have a size of less than 1000 nanometers. The nanoparticles comprise gold, silver, copper, indium, palladium, aluminum, iron, cobalt, nickel, an alloy thereof, an oxide thereof, or a mixture thereof. The metal nanowires are in an amount of from 1 to 11 percent by weight, while the plurality of nanoparticles are in an amount of from 0.5 to 4 percent based upon the total weight of the electromagnetic shielding composition taken as 100 percent by weight such that the shielding effectiveness of the composition is greater than 10 dB.
In yet another embodiment, an electromagnetic shielding composition is provided. The electromagnetic shielding composition comprises a carrier, a plurality of metal nanowires, and a plurality of nanoparticles. The plurality of metal nanowires are dispersed within the carrier. The plurality of metal nanowires have an aspect ratio of from 20 to 500. The metal nanowires comprise gold, silver, copper, indium, palladium, aluminum, iron, cobalt, nickel, an oxide thereof, or a mixture thereof. The plurality of nanoparticles are dispersed within the carrier. The nanoparticles have a size of from 30 to 1000 nanometers. The nanoparticles comprise gold, silver, copper, indium, palladium, aluminum, iron, cobalt, nickel, an alloy thereof, an oxide thereof, or a mixture thereof, wherein the metal nanowires are in an amount of from 1 to 3 percent by weight, while the plurality of nanoparticles are in an amount of from 0.5 to 4 percent based upon the total weight of the electromagnetic shielding composition taken as 100 percent by weight such that the shielding effectiveness of the composition is greater than 10 dB.
One embodiment of the present disclosure discloses an electromagnetic shielding device, which includes a body member and a thin film. The thin film is formed on a surface of the body member for shielding electromagnetic radiation. The thin film comprises a plurality of metal nanowires dispersed within the thin film and being in an amount of between 1 and 95 percent by weight of the thin film and a plurality of nanoparticles dispersed within the thin film and being in an amount of between 0.1 and 60 percent by weight of the thin film.
One embodiment of the present disclosure further provides an anti-electrostatic device, which comprises a substrate and a thin film formed on the substrate. The thin film includes a plurality of metal nanowires dispersed within the thin film and being in an amount of between 1 and 95 percent by weight of the thin film taken as 100 percent and a plurality of nanoparticles dispersed within the thin film and being in an amount of between 0.1 and 60 percent by weight of the thin film taken as 100 percent.
The disclosure further provides a method of manufacturing an electromagnetic shielding structure. The method comprises the steps of: providing a target; providing a mixture comprising a plurality of metal nanowires having aspect ratios greater than 50; forming a first thin film on a surface of the target using the mixture; and heating the first thin film at a temperature in a range of from 50 to 250 degrees Celsius.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and, together with the description, serve to explain the principles of the invention.
One embodiment of the disclosure provides an electromagnetic shielding composition comprising a carrier, a plurality of metal nanowires, and a plurality of nanoparticles. The plurality of metal nanowires are dispersed within the carrier. The plurality of nanoparticles are dispersed within the carrier. The plurality of metal nanowires and the plurality of nanoparticles are mixed with each other.
In one embodiment, the plurality of metal nanowires is in an amount of from 1 to 95 percent based on the total weight of the electromagnetic shielding composition taken as 100 percent by weight, and the plurality of nanoparticles are in an amount of between 0.1 and 60 percent based on the total weight of the electromagnetic shielding composition taken as 100 percent by weight. In another embodiment, the nanoparticles are in an amount of between 0.3 and 40 percent. In another embodiment, the nanoparticles are in an amount of between 0.5 and 20 percent. In another embodiment, the nanoparticles are in an amount of between 0.5 and 4 percent by weight. In another embodiment, the nanoparticles are in an amount of between 0.5 and 2 percent by weight.
In one embodiment, the plurality of metal nanowires are in an amount of between 1 and 95 percent based upon the total weight of the electromagnetic shielding composition taken as 100 percent by weight, and the plurality of nanoparticles are in an amount of between 0.5 and 60 percent based upon the total weight of the electromagnetic shielding composition taken as 100 percent by weight.
In one embodiment, the content ratio of the metal nanowires to the nanoparticles can be greater than 0.1.
One embodiment of the disclosure provides a solid body solidified from the above-mentioned composition. In one embodiment, the above-mentioned solid body can be a thin film of an electromagnetic shielding device or on an anti-electrostatic device. The metal nanowires can be formed as an electrically conductive structure so that the solid body can substantially conduct electricity.
In theory, the existence of nanoparticles can change optical path length difference; so electromagnetic energy may be dissipated within the interior of the solid body. Thus, mixing the nanoparticles with the metal nanowires can obviously improve the electromagnetic shielding effectiveness.
The sizes of the nanoparticles disclosed in the present invention can be less than 1000 nanometers.
In one embodiment, the nanoparticle can be an electrically conductive nanoparticle. In another embodiment, the nanoparticle can be a metal nanoparticle, the material of which can be gold, silver, copper, indium, palladium, aluminum, iron, cobalt, nickel, an alloy thereof, an oxide thereof, or mixture thereof, wherein the metal nanoparticles comprise between 0.5 and 2 percent based upon the total by weight of the electromagnetic shielding composition taken as 100 percent. In another embodiment, the nanoparticles may be gold-coated silver nanoparticles, silver-coated gold nanoparticles, gold-coated copper nanoparticles, copper-coated gold nanoparticles, silver-coated copper nanoparticles, copper-coated silver nanoparticles, or a combination thereof.
In one embodiment, the nanoparticle can be a magnetic nanoparticle, which can include magnetic iron. In another embodiment, the nanoparticle may be an insulated magnetic nanoparticle, which may include iron oxide or ferrous ferric oxide (Fe3O4), wherein the insulated magnetic nanoparticles can comprise between 0.5 and 4 percent or between 0.5 and 2 percent based upon the total weight of the electromagnetic shielding composition taken as 100 percent.
In one embodiment, the nanoparticles are electrically conductive particles, magnetic particles, insulated magnetic particles, or a mixture thereof.
In one embodiment, the nanoparticles can be nanoparticles of silver, iron oxide, or a mixture thereof, wherein the nanoparticles can comprise between 0.5 and 4 percent or between 0.5 and 2 percent based upon the total weight of the electromagnetic shielding composition taken as 100 percent.
In one embodiment, the diameters of the nanoparticles can be larger than 10 nanometers, or between 30 nanometers and 1000 nanometers. In one embodiment, the diameters of the nanoparticles can be in a range of from 30 nanometers to 500 nanometers.
As the above-mentioned composition is solidified as a solid body, the plurality of metal nanowires can be uniformly dispersed within the solid body. In one embodiment, the plurality of metal nanowires can be formed into a network structure in the solid body so as to make the solid body have low surface resistivity, for example, less than 10 ohms per square (Ω/sqr).
In another embodiment, the composition may include a small quantity of metal nanowires, and after the composition is solidified to a solid body, the metal nanowires are formed into a network or network-like structure, wherein the network or network-like structure renders the solid body to have high surface resistivity, for example, greater than 10 to 106 ohms per square.
In another embodiment, the composition may include a small quantity of metal nanowires, and after the composition is solidified to a solid body, the metal nanowires are formed into a network or network-like structure, wherein the network or network-like structure renders the solid body to have high surface resistivity, for example, greater than 104 to 1012 ohms per square. As such, the solid body can be used for anti static electricity products.
The composition may include nanowires with high aspect ratios. Using the metal nanowires with high aspect ratios can significantly increase the level of the electromagnetic shielding effectiveness of the solid body. Further, using the metal nanowires with high aspect ratios can reduce the amount of use of the metal fillers.
In one embodiment, the metal nanowires can have aspect ratios of greater than 10, or, for example, between 20 and 500, or, for example, between 50 and 300.
In one embodiment, the material of the metal nanowire can be gold, silver, copper, indium, palladium, aluminum, iron, cobalt, nickel, an alloy thereof, an oxide thereof, or a mixture thereof. In another embodiment, the metal nanowires may be gold-coated silver metal nanowires, silver-coated gold metal nanowires, gold-coated copper metal nanowires, copper-coated gold metal nanowires, silver-coated copper metal nanowires, copper-coated silver metal nanowires, or a combination thereof.
The carrier can be a polymer, which includes thermoplastic resins such as acrylic resins or thermosetting resins such as epoxy resins. In one embodiment, the carrier can be a photo-cross-linking or a thermally cross-linking polymer.
Employing a mixture including metal nanoparticles or nanoparticles with high permeability constant to form a thin film on a target can cause the target to exhibit improved shielding effectiveness. If the thin film is treated with light energy or heat energy, the shielding effectiveness of the thin film can be further improved. Due to improved shielding effectiveness, the thickness of the thin film can be reduced while maintaining the same necessary level of shielding effectiveness. A thin film with a reduced thickness can be more uniform and consume less material. The thin film can be heated to a temperature in a range of from 50 to 250 degrees Celsius. The mixture can include nano-material and a carrier, wherein the carrier can include a polymer, and the nano-material can include metal nanowires, which can have aspect ratios of greater than 50. In one embodiment, the carrier can be a photo-cross-linking or a thermally cross-linking polymer.
The thin film can be heated to a temperature of from 50 to 250 degrees Celsius for a period of time (at least 5 minutes). As such, the shielding effectiveness of the thin film can be improved by at least 5 dB at frequencies of from 30 MHz and 16 GHz. In one embodiment, the thin film is heated to a temperature in a range of from 60 to 250 degrees Celsius for at least 5 minutes. In another embodiment, the heating time is above at least one hour. In one embodiment, the thin film is heated to a temperature of from 60 to 200 degrees Celsius for a period of from 5 minutes to 2 hours.
The metal nanowires may comprise gold, silver, copper, indium, palladium, aluminum, iron, cobalt, nickel, a mixture thereof, or an oxide thereof.
In one embodiment, the thin film can further comprise a plurality of nanoparticles, wherein the nanoparticles can be metal nanoparticles, nanoparticles with high permeability constant, or a mixture thereof. The metal nanoparticles can be silver nanoparticles. The nanoparticles with high permeability constant can be nanoparticles of iron oxide. The nanoparticles can have a size of less than 1000 nanometers (i.e., between 30 nanometers and 1000 nanometers or between 30 nanometers and 500 nanometers). The nanoparticles can comprise from 0.1 to 60 percent by weight, from 0.3 to 40 percent by weight, from 0.5 to 20 percent by weight, from 0.5 to 4 percent by weight, or from 0.5 to 2 percent by weight, based upon the total weight of the thin film taken as 100 percent by weight.
The target can have two thin films formed thereon and stacked on each other, wherein one thin film includes metal nanowires while another thin film includes metal nanoparticles or nanoparticles with high permeability constant.
The target depends on the application of the mixture. For example, when the mixture is used on electronic devices, the target may be the shell of the electronic devices, the printed circuit board of the electronic devices, or the components that need EMI protection in the electronic devices. In addition, the target can also be a substrate carrying a thin film.
Several examples are provided as follows for detailed explanation of the present disclosure.
The method described below can be used in formulating compositions including different types or contents of metal nanowires and nanoparticles. Initially, for each sample, silver nanowires are grown to have an aspect ratio of greater than 20 using a method such as the laser ablation method, the metal vapor synthesis method, the chemical reduction method, or the polyol method. The above-mentioned methods are well-known in the art; thus the detailed processes are not described here.
Subsequently, silver nanowires and nanoparticles are added into a polymer material to obtain a composition. The composition can be stirred using an ultrasonic vibrator and a planetary centrifugal mixer so as to disperse the silver nanowires and the nanoparticles within the polymer material. Thereafter, the composition is solidified to a solid body with a desirable shape. Finally, the electromagnetic shielding effectiveness of the solid body is tested. The electromagnetic shielding effectiveness test method can be a standard electromagnetic shielding effectiveness test method such as ASTM D4935-99. Usually, the shielding effectiveness (S.E.) can be obtained using the following equation:
where Iin is the strength of electromagnetic radiation incident on a test sample, and Iout is the strength of electromagnetic radiation through the test sample.
Table 1 below shows 6 compositions of different concentrations. Compositions (Samples 1 to 5) are prepared by adding the same weight percentage of silver nanowire (AgNW) and different weight percentages of iron oxide nanoparticles (Fe3O4NP) into a polymer material, wherein based on the total weight of the composition taken as 100 percent, the silver nanowires comprise 1.22 percent by weight of the composition, and the iron oxide nanoparticles comprise between 0 and 1.88 percent by weight of the composition. The polymer material can be ETERSOL 6515 unsaturated polyester manufactured by ETERNAL CHEMICAL Co., Ltd., Taiwan.
The polymer material includes polymethyl methacrylate solution. The polymethyl methacrylate can comprise from 45 to 55 percent by weight of the polymer material, and water can comprise from 45 to 55 percent by weight of the polymer material.
The aspect ratio of the silver nanowires can be 250, and the diameter of the iron oxide nanoparticle can be 100 nanometers. Sample 6 is prepared by mixing only iron oxide nanoparticles with the polymer material, wherein the concentration of the iron oxide nanoparticles is around 9.09 percent by weight. After Samples 1 to 6 are individually uniformly mixed, Samples 1 to 6 are used to separately form a thin film with a thickness of 50 micrometers. Finally, the electromagnetic shielding effectiveness of these thin films is tested.
As shown in
From the above test results, it can be seen that the addition of a suitable amount of magnetically permeable dielectric nanoparticles to a thin film including metal nanowires can obviously improve the electromagnetic shielding effectiveness. However, if a high amount of permeable constant nanoparticles is added to a thin film including metal nanowires, the electromagnetic shielding effectiveness of the thin film decreases, contrary to the expectation, based on prior art knowledge, that the electromagnetic shielding effectiveness would be greater if more permeable constant nanoparticles are added. Therefore, when iron oxide nanoparticles have particle diameters of from 80 to 120 nanometers and silver nanowires have aspect ratios in a range of from 200 to 300, the amount of the iron oxide nanoparticles can be in a range of from 0.1 to 3 percent by weight, preferably in a range of from 0.5 to 2 percent by weight.
In addition, from the test result for Sample 6, it can be seen that although iron oxide nanoparticles are magnetically permeable dielectric nanoparticles, the thin film including 9.09 percent by weight of iron oxide nanoparticles has almost no electromagnetic shielding effect. The test result for Sample 6 teaches that the addition of iron oxide nanoparticles in an amount of less than 9.09 weight percent to a thin film including metal nanowires should not improve the electromagnetic shielding effectiveness of the thin film. However, from the results of the experiments of the disclosure, it can be found that the addition of a low amount of iron oxide nanoparticles to a thin film including metal nanowires can unexpectedly improve the electromagnetic shielding effectiveness of the thin film.
Table 2 below shows compositions (Samples 7 to 9) each including based on the total weight of the composition taken as 100 percent, silver nanowires in a concentration of 1.22 percent by weight and iron oxide nanoparticles in a specific amount ranging from 0 to 1.24 percent by weight, wherein the silver nanowire has an aspect ratio of 80, and the diameter of the iron oxide nanoparticle is around 100 nanometers. After mixing, Samples 7 to 9 are used to separately form a thin film with a thickness of 50 micrometers and the electromagnetic shielding effectiveness of these thin films is tested.
Each composition includes a polymer material that includes polymethyl methacrylate solution. Based on the total weight of the polymer material taken as 100 percent, Polymethyl methacrylate can comprise from 45 to 55 percent by weight of the polymer material, and water can comprise from 45 to 55 percent by weight of the polymer material.
As shown in
For example, the thin film formed using Sample 4 exhibits electromagnetic shielding effectiveness of from 38 to 58 dB over a frequency range of from 2 to 16 GHz. In comparison, over the same frequency, the thin film formed using Sample 8 has electromagnetic shielding effectiveness in an acceptable range of from 20 to 27 dB.
In addition to the influence of the aspect ratio of a silver nanowire, similar to the results of the afore-mentioned experiments, thin films formed with Samples 7 to 9 having higher concentration of iron oxide nanoparticles exhibit higher electromagnetic shielding effectiveness.
Furthermore, the thin film formed using Sample 4 exhibits electromagnetic shielding effectiveness of from 38 to 58 dB over a frequency range of from 2 to 16 GHz. In comparison, as shown in
Table 3 below shows compositions (Samples 10 to 13), each of which includes 1.14 percent by weight of silver nanowires and iron oxide nanoparticles in a specific amount ranging from 0 to 1.99 percent by weight based on the total weight of the composition taken as 100 percent, wherein the silver nanowires have an aspect ratio of 250, and the diameters of the iron oxide nanoparticles are around 100 nanometers. After mixing, Samples 10 to 13 are used to separately form a thin film with a thickness of 50 micrometers for testing electromagnetic shielding effectiveness. The compositions include a polymer material that includes polymethyl methacrylate solution. Based on the total weight of the polymer material taken as 100 percent, Polymethyl methacrylate can comprise from 45 to 55 percent by weight of the polymer material, and water can comprise from 45 to 55 percent by weight of the polymer material.
As shown in
From the results of Experiment 3, it can be seen that compared to the thin film without iron oxide nanoparticles, the thin film with 1.33 percent by weight of iron oxide nanoparticles can have significantly improved electromagnetic shielding effectiveness. Similarly, the addition of too many iron oxide nanoparticles, such as the 1.99 percent by weight of iron oxide nanoparticles in Sample 13, may have adverse impact on the electromagnetic shielding effectiveness.
As a result, according to the results from Samples 4 and 5 and Samples 11, 12 and 13, the electromagnetic shielding effectiveness of a thin film including nanowires in an amount of less than 3 percent by weight cannot be improved by adding nanoparticles in an amount of more than 2 percent by weight. Therefore, when iron oxide nanoparticles are between 80 to 120 nanometers in diameter, silver nanowires have aspect ratios of from 200 to 300, and the thin film includes nanowires of from 1.0 to 1.3 percent by weight, the concentration of the iron oxide nanoparticles is preferably in a range of from 0.1 to 3 percent by weight, more preferably in a range of from 0.2 to 2 percent by weight, and most preferably in a range of from 1 to 2 percent by weight.
Table 4 below shows compositions (Samples 14 to 17) each including 3 percent by weight silver nanowires and iron oxide nanoparticles in a specific amount in a range of from 0 to 1.79 percent by weight based on the total weight of the composition taken as 100 percent, wherein the silver nanowires have an aspect ratio of 250, and the diameters of the iron oxide nanoparticles are around 0.5 micrometers. After mixing, Samples 14 to 17 are used to separately form a thin film with a thickness of 50 micrometers for testing electromagnetic shielding effectiveness. The compositions include a polymer material that includes polymethyl methacrylate solution. Based on the total weight of the polymer material taken as 100 percent, Polymethyl methacrylate can comprise from 45 to 55 percent by weight of the polymer material, and water can comprise from 45 to 55 percent by weight of the polymer material.
As illustrated in
For example, in comparison of Sample 5 and Sample 17, the thin film formed with Sample 5 exhibits electromagnetic shielding effectiveness of from 36 to 53 dB over a frequency range of from 6 to 16 GHz, while the thin film formed with Sample 17 exhibits low electromagnetic shielding effectiveness of from 9 to 52 dB over the same frequency range. With the increase of the concentration of nanowires, the increase of the diameters of nanoparticles, in a similar concentration can exhibit significant effect over high frequency spectrum.
In addition, as shown in
In addition, as indicated by the experiment results shown in
Table 5 below shows compositions (Samples 18 to 21) each including 10.45 percent by weight silver nanowires and iron oxide nanoparticles in a specific amount of from 0 to 1.87 percent by weight based on the total weight of the composition taken as 100 percent, wherein the silver nanowires have an aspect ratio of 250 and the diameters of the iron oxide nanoparticles are around 30 nanometers. After mixing, Samples 18 to 21 are used to separately form a thin film with a thickness of 50 micrometers for testing electromagnetic shielding effectiveness. The compositions include a polymer material that includes polymethyl methacrylate solution. Based on the total weight of the polymer material taken as 100 percent, Polymethyl methacrylate can comprise from 45 to 55 percent by weight of the polymer material, and water can comprise from 45 to 55 percent by weight of the polymer material.
As illustrated in
For example, in comparison of Sample 5 and Sample 21, the thin film formed with Sample 5 exhibits electromagnetic shielding effectiveness of 36 to 48 dB over a frequency range of 4 to 16 GHz, while the thin film formed with Sample 21 exhibits low electromagnetic shielding effectiveness of 25 to 37 dB over the same frequency range.
Further, as indicated by the electromagnetic shielding effectiveness test results for the thin films formed with Samples 18 to 21, the electromagnetic shielding effectiveness is improved with the increase of the content of iron oxide nanoparticles, whereas compared with the thin film without including iron oxide nanoparticles, the thin film including 1.87 percent by weight iron oxide nanoparticles has preferable electromagnetic shielding effectiveness. Therefore, when iron oxide nanoparticles are from 10 to 50 nanometers in diameter, silver nanowires have aspect ratios of 200 to 300, and the thin film includes nanowires in a concentration of 10.45 percent by weight, the amount of the iron oxide nanoparticles is preferably from 0.4 to 2.6 percent by weight, more preferably from 0.6 to 2.4 percent by weight, and most preferably from 1 to 2 percent by weight.
Thus, as shown in
Table 6 below shows compositions (Samples 22 to 25) each including 1.14 percent by weight silver nanowires and silver nanoparticles in a specific amount of from 0 to 1.99 percent by weight based on the total weight of the composition taken as 100 percent, and Sample 26 which includes 7.65 percent by weight silver nanoparticles and does not include silver nanowires, wherein the silver nanowire has an aspect ratio of 250 and the diameter of the silver nanoparticle is around 100 nanometers. After mixing, Samples 22 to 26 are used to separately form a thin film with a thickness of 50 micrometers for testing electromagnetic shielding effectiveness. The compositions include a polymer material that includes polymethyl methacrylate solution. Based on the total weight of the polymer material taken as 100 percent, Polymethyl methacrylate can comprise from 45 to 55 percent by weight of the polymer material, and water can comprise from 45 to 55 percent by weight of the polymer material.
As illustrated in
For example, in comparison of Sample 12 and Sample 24, the thin film formed with Sample 12 exhibits electromagnetic shielding effectiveness of 18 to 29 dB over the demonstrated frequency range, while the thin film formed with Sample 29 exhibits electromagnetic shielding effectiveness of 19 to 30 dB over the same frequency range. Both samples exhibit nearly identical electromagnetic shielding effectiveness except around the frequency of 4.8 GHz, at which a resonant mode occurs with the thin film formed with Sample 24. According to the above-mentioned experiment results, thin films added with silver nanoparticles and thin films added with magnetically permeable dielectric nanoparticles exhibit identical electromagnetic shielding effectiveness.
Therefore, when silver nanoparticles are from 80 to 120 nanometers in diameter and silver nanowires have aspect ratios of 200 to 300, the amount of the silver nanoparticles is preferably in a range of 0.5 to 2.5 percent by weight, and more preferably in a range of 0.7 to 2 percent by weight.
Further, in comparison of electromagnetic shielding effectiveness test results for the thin films formed with Samples 22 to 25, the electromagnetic shielding effectiveness of the thin film including only nanowires is better than that of the thin film including only nanoparticles. The electromagnetic shielding effectiveness is improved with the increase of the content of silver nanoparticles, and if electrically conductive nanoparticles are used to replace magnetically permeable nanoparticles, both types of thin films can have a certain level of electromagnetic shielding effectiveness.
Thin films formed using the presently disclosed composition including nanowires and nanoparticles can exhibit excellent electromagnetic shielding effectiveness.
As shown in Table 7 and
Referring to
Referring to
In summary, the addition of a suitable amount of nanoparticles to a composition including metal nanowires can improve the electromagnetic shielding effectiveness of the thin film formed using the composition. According to the results of the above-mentioned experiments, it is believed that based on the total weight of the composition taken as 100 percent, the concentration of the metal nanowires can be in a range of from 1 to 95 percent by weight. Preferably, the amount of the metal nanowires can be from 1 to 11 percent by weight. More preferably, the amount of the metal nanowires can be from 1 to 3 percent by weight. Furthermore, the amount of magnetically permeable or metal nanoparticles can be in a range of from 0.1 to 60 percent by weight, from 0.1 to 10 percent by weight, from 0.5 to 10 percent by weight, or from 0.5 to 2 percent by weight.
In addition, the addition of large amounts of magnetically permeable or metal nanoparticles to the composition including metal nanowires cannot significantly contribute to the improvement of the electromagnetic shielding effectiveness. Further, compared with the thin films added with metal nanowires or metal nanoparticles for increasing electrical conductivity, the thin films added with magnetically permeable nanoparticles can exhibit better improvement of the electromagnetic shielding effectiveness.
Referring back to
Conventionally, the shielding effectiveness and the conductivity are positively correlated. However, according to the experiment results for Samples 31 and 32, it can be seen that when electrically conductive material is added to a certain critical level, the change of the electrically conductive is limited.
Samples 31 and 32 comprise a polymer material including polyurethane and water, wherein based on the total weight of the polymer material taken as 100 percent, the polyurethane comprises from 45 to 55 percent by weight of the polymer material, and the water comprises from 45 to 55 percent by weight of the polymer material.
In summary, the disclosure provides a method of thermally treating an electromagnetic shielding film including nano-material so as to increase the shielding effectiveness of the thin film. Therefore, the thickness of the thin film can be reduced while not compromising its shielding effectiveness.
The above-described exemplary embodiments are intended to be illustrative only. Those skilled in the art may devise numerous alternative embodiments without departing from the scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 099116931 | May 2010 | TW | national |
| 100105049 | Feb 2011 | TW | national |
| 201110130025.X | May 2011 | CN | national |
