CN114424684A - Electromagnetic wave shielding material - Google Patents
Electromagnetic wave shielding material Download PDFInfo
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- CN114424684A CN114424684A CN202080066577.6A CN202080066577A CN114424684A CN 114424684 A CN114424684 A CN 114424684A CN 202080066577 A CN202080066577 A CN 202080066577A CN 114424684 A CN114424684 A CN 114424684A
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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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/16—Making metallic powder or suspensions thereof using chemical processes
- B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
- B22F9/24—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C19/00—Alloys based on nickel or cobalt
- C22C19/03—Alloys based on nickel or cobalt based on nickel
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
- H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
- H01F1/147—Alloys characterised by their composition
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- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
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- Microelectronics & Electronic Packaging (AREA)
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- Shielding Devices Or Components To Electric Or Magnetic Fields (AREA)
Abstract
The present invention provides an electromagnetic wave shielding material having excellent electromagnetic wave shielding properties, particularly excellent electromagnetic wave absorption properties, in a high frequency region (particularly, quasi-millimeter waves and millimeter waves) of several tens of GHz. The present invention relates to an electromagnetic wave shielding material comprising nanowires composed of iron and nickel.
Description
Technical Field
The present invention relates to an electromagnetic wave shielding material having excellent electromagnetic wave shielding properties, particularly excellent electromagnetic wave absorption properties, in a high-frequency region of several tens of GHz.
Background
In recent years, in 5 th generation mobile communication systems and advanced driving assistance systems, use of radio waves in the quasi-millimeter wave and millimeter wave regions has been rapidly performed. In the 5 th generation mobile communication system, radio communication is performed using radio waves of frequencies such as n257 (26.50-29.50 GHz), n258 (24.25-27.50 GHz), n259 (39.5-43.50 GHz), n260 (37.00-40.00 GHz), and n261 (27.50-28.35 GHz). In the millimeter wave radar which is a part of the advanced driving assistance system, as a 24GHz band narrow band radar system, a radio beam of a frequency of 24.05-24.25 GHz is used, as a 24GHz/26GHz band UWB radar system, a radio beam of a frequency of 24.25-29.0 GHz is used, as a 60GHz band millimeter wave radar system, a radio beam of a frequency of 60.0-61.0 GHz is used, as a 76GHz band millimeter wave radar system, a radio beam of a frequency of 76.0-77.0 GHz is used, as a 79GHz band high resolution radar system, a radio beam of a frequency of 77.0-81.0 GHz is used to perform sensing of the periphery of the vehicle. Unlike conventional products which have been strongly maintained, electronic components of millimeter wave radars of 5 th generation mobile communication systems and advanced driving support systems are required to have an electromagnetic wave shielding material suitable for them in order to suppress the generation and influence of noise including radio waves in the quasi-millimeter wave and millimeter wave regions.
Conventionally, the main stream of EMC (electromagnetic compatibility) of electronic devices is to cover the device itself with a conductive body such as a metal case. However, with the use of quasi-millimeter waves and millimeter waves in the 5 th generation mobile communication system and the advanced driving assistance system, the miniaturization and high integration of electronic components, and the like, a phenomenon called autopoisoning (internal EMC) in which the characteristics of electronic components such as semiconductors are degraded due to noise generated inside the devices and the like becomes a problem. In order to suppress autotoxicity, a material that absorbs radio waves is desired instead of a conventional conductor.
As an electromagnetic wave shielding material (electromagnetic wave absorber) absorbing quasi-millimeter waves and millimeter wave bands, a Metamaterial (Metamaterial) electromagnetic wave absorber is known, but the absorbing frequency band is extremely narrow, which is less than 0.1GHz, and is not suitable for a system which performs large-capacity wireless communication using a wide frequency band, such as a 5 th generation mobile communication system and a millimeter wave radar of an advanced driving assistance system. In addition, an electromagnetic wave shielding material using nickel nanowires is disclosed in cited document 1. However, the electromagnetic wave shielding material of cited document 1 has insufficient shielding performance, and has a problem particularly in absorption of an electromagnetic wave.
Documents of the prior art
Patent document
Patent document 1: japanese patent laid-open publication No. 2017-165996.
Disclosure of Invention
The present invention provides an electromagnetic wave shielding material having excellent electromagnetic wave shielding properties, particularly excellent electromagnetic wave absorption properties, in a high-frequency region (particularly, a quasi-millimeter wave region and a millimeter wave region) of several tens of GHz.
The present inventors have found that a material containing nanowires made of iron and nickel achieves the above object, and have completed the present invention.
That is, the gist of the present invention is as follows.
(1) An electromagnetic wave shielding material includes nanowires composed of iron and nickel.
(2) The electromagnetic wave shielding material according to (1), wherein the nanowires have a mass ratio of iron to nickel (iron/nickel) of 20/80 to 65/35.
(3) The electromagnetic wave shielding material according to (1) or (2), further comprising a dielectric.
(4) The electromagnetic wave shielding material according to (3), wherein the dielectric is an adhesive.
(5) The electromagnetic wave shielding material according to (3) or (4), wherein the ratio of the nanowire to the total of the nanowire and the dielectric is 10% by mass or more and less than 65% by mass.
(6) The electromagnetic wave shielding material according to (3) or (4), wherein the ratio of the nanowire to the total of the nanowire and the dielectric is 40 to 60% by mass.
(7) The electromagnetic wave shielding material according to any one of (1) to (6), wherein the volume resistivity is 10－2Omega cm or more.
(8) A dispersion liquid comprising the electromagnetic wave shielding material according to any one of (1) to (7).
(9) A sheet comprising the electromagnetic wave shielding material according to any one of (1) to (7).
(10) A film comprising the electromagnetic wave shielding material according to any one of (1) to (7).
(11) An electronic component comprising the electromagnetic wave shielding material according to any one of (1) to (7).
According to the present invention, an electromagnetic wave shielding material excellent in electromagnetic wave shielding properties, particularly electromagnetic wave absorption properties, in a high frequency region (particularly, quasi-millimeter wave region and millimeter wave region) of several tens of GHz can be provided.
The electromagnetic wave shielding material of the present invention can be applied to electronic components and the like of 5 th generation mobile communication systems, advanced driving assistance systems, and the like.
Drawings
Fig. 1 is a diagram showing the electromagnetic wave absorbability in the K band of example 1.
FIG. 2 is a graph showing the Ka-band electromagnetic wave absorbability in example 1.
Fig. 3 is a diagram showing the U-band electromagnetic wave absorbability in example 1.
Fig. 4 is a diagram showing the electromagnetic wave absorbability in the E band of example 1.
Fig. 5 is a diagram showing the electromagnetic wave shielding properties in the K band of example 1.
Fig. 6 is a view showing the Ka band electromagnetic wave shielding properties of example 1.
Fig. 7 is a diagram showing the U-band electromagnetic wave shielding performance of example 1.
Fig. 8 is a diagram showing the electromagnetic wave shielding properties in the E band of example 1.
FIG. 9 is a graph showing the K-band electromagnetic wave absorbability in example 5.
FIG. 10 is a graph showing the Ka-band electromagnetic wave absorbability in example 5.
Fig. 11 is a diagram showing the U-band electromagnetic wave absorbability in example 5.
FIG. 12 is a graph showing the E-band electromagnetic wave absorbability in example 5.
Fig. 13 is a diagram showing the electromagnetic wave shielding properties in the K band of example 5.
FIG. 14 is a view showing the Ka-band electromagnetic wave shielding properties of example 5.
Fig. 15 is a diagram showing the U-band electromagnetic wave shielding performance of example 5.
Fig. 16 is a diagram showing the electromagnetic wave shielding properties in the E band of example 5.
Fig. 17 is a graph showing the electromagnetic wave absorbability in the K band of comparative example 2.
FIG. 18 is a graph showing the Ka band electromagnetic wave absorbability in comparative example 2.
Fig. 19 is a diagram showing the U-band electromagnetic wave absorbability in comparative example 2.
Fig. 20 is a diagram showing the electromagnetic wave absorbability in the E band of comparative example 2.
Fig. 21 is a diagram showing the electromagnetic wave shielding properties in the K band of comparative example 2.
Fig. 22 is a view showing the Ka band electromagnetic wave shielding properties of comparative example 2.
Fig. 23 is a diagram showing the U-band electromagnetic wave shielding performance of comparative example 2.
Fig. 24 is a diagram showing the electromagnetic wave shielding properties in the E band of comparative example 2.
Detailed Description
The electromagnetic wave shielding material of the present invention comprises nanowires composed of iron and nickel.
In the present invention, the electromagnetic wave shielding (Shield) property refers to a property that takes into consideration both a property of reflecting electromagnetic waves (electromagnetic wave reflectivity) and a property of absorbing electromagnetic waves (electromagnetic wave absorbability). Electromagnetic wave reflectivity is a property of reflecting an electromagnetic wave in the direction of an incident surface of the electromagnetic wave to suppress transmission of the electromagnetic wave to the opposite surface. Electromagnetic wave absorbability is a property of converting energy of an electromagnetic wave into magnetism and heat to suppress the electromagnetic wave transmitted to the opposite side. The electromagnetic wave shielding property and the electromagnetic wave absorption property can be measured by a free space method. In the present specification, a high frequency band of several tens of GHz means a frequency region of 18 to 110GHz (particularly 24.05 to 81.0 GHz). The quasi millimeter wave is a frequency band of 20-30 GHz. The millimeter wave is a frequency band of 30-300 GHz.
The nanowires used in the present invention are fibrous with an average diameter of less than 1 μm. From the viewpoint of ease of production of the electromagnetic wave shielding material and further improvement of electromagnetic wave shielding properties, particularly electromagnetic wave absorption properties, the nanowires preferably have an average diameter of 50 to 900nm and an average length of 5 μm or more (particularly 10 μm or more), more preferably have an average diameter of 70 to 700nm and an average length of 15 to 500 μm. The aspect ratio of the nanowire used in the present invention is usually 10 or more (particularly 50 or more), and from the viewpoint of further improving the electromagnetic wave shielding property (particularly, electromagnetic wave absorption property), it is preferably 10 to 1000, and more preferably 50 to 500.
In the present specification, the aspect ratio of the nanowires is calculated from an image captured by SEM (scanning electron microscope) to obtain the value of the major axis (length)/minor axis (diameter) of each nanowire, and the average value of the values of 100 nanowires is used.
The form of iron and nickel constituting the nanowire is not particularly limited, and examples thereof include a structure in which iron and nickel are randomly arranged, a core-sheath structure in which nickel is arranged around iron, a core-sheath structure in which iron is arranged around nickel, and a particle chain structure of iron particles and nickel particles. Among them, from the viewpoint of improving electromagnetic wave shielding properties, particularly electromagnetic wave absorption properties, a structure in which iron and nickel are randomly arranged is preferable.
The mass ratio of iron to nickel (iron/nickel) of the nanowire is not particularly limited. The mass ratio of iron to nickel is preferably 20/80 to 65/35, more preferably 20/80 to 50/50, further preferably 20/80 to 40/60, and particularly preferably 20/80 to 30/70, and the mass ratio of permalloy a (iron: nickel: 21.5: 78.5 (mass ratio)) is most preferable in order to further increase the magnetic permeability, because the magnetic material is advantageous in absorbing electromagnetic waves.
The method for producing the nanowires used in the present invention is not particularly limited, and examples thereof include a method in which an iron salt and a nickel salt are reduced in a reaction solution to prepare a nanowire dispersion, and then the nanowires are recovered.
Examples of the method for producing the nanowire dispersion by reducing an iron salt and a nickel salt in a reaction solution include an electrolytic method using a positive electron oxide film and a liquid phase reduction method. The liquid phase reduction method is a method of obtaining a dispersion by reducing an iron salt and a nickel salt in a reaction solution while applying a magnetic field. Among them, the latter method is preferable in terms of being able to be produced at a relatively low cost.
The iron salt and the nickel salt are preferably chloride or acetate, and chloride is more preferable from the viewpoint of dispersibility of the obtained dispersion. Specifically, iron (II) chloride and iron (II) chloride tetrahydrate are preferable as the iron salt, and nickel chloride hexahydrate are preferable as the nickel salt.
The total concentration of the iron salt and the nickel salt in the reaction solution is preferably 10 to 1000. mu. mol/g, more preferably 10 to 500. mu. mol/g, and still more preferably 15 to 85. mu. mol/g, from the viewpoint of controlling the shape of the obtained nanowire and improving the yield.
From the viewpoint of controlling the shape of the obtained nanowire and improving the yield, it is preferable to add citrate to the reaction solution. The amount of citrate to be added is preferably 0.5 to 5 mol%, more preferably 0.5 to 3 mol%, based on the total of the iron salt and the nickel salt.
The reaction solvent used in the reaction solution is preferably a highly polar reaction solvent, and examples thereof include water, alcohols, and glycols. Ethylene glycol having a high boiling point and viscosity is preferable from the viewpoint of stability of generated gas with respect to the temperature of the reduction reaction.
In the present invention, the liquid property of the solution for the reduction reaction is important, and the reduction reaction does not proceed in an acidic to neutral region, and nanowires are not produced. Therefore, the solution for the reduction reaction needs to be alkaline in liquid property. The liquid properties of the solution may be adjusted by adding a basic compound, specifically, by adding a basic compound such as sodium hydroxide or potassium hydroxide. The amount of the basic compound to be added is preferably 1mol or less based on 1mol of the total of the iron salt and the nickel salt, and is preferably 0.2 to 1mol, more preferably 0.5 to 0.8mol, from the viewpoints of reducing reactivity of the iron salt and the nickel salt, controlling the shape of the obtained nanowire, and improving the yield. The basic compound is preferably dissolved in the reaction solvent.
If sodium hydroxide and potassium hydroxide are added, they react with iron ions and nickel ions generated from the respective salts to produce a coprecipitate of salts containing iron and nickel. The coprecipitate is not easily reduced, and therefore, there are problems such as a significant delay in the reduction reaction and the formation of scale-like and irregular particles. In the present invention, it is preferable to add ammonia to complex the coprecipitate with an amine in order to redissolve the coprecipitate. The amount of ammonia added is preferably 3 to 30mol based on 1mol of the basic compound, and is preferably 10 to 30mol, more preferably 20 to 30mol, from the viewpoints of reducing reactivity of iron ions and nickel ions, controlling the shape of the obtained nanowire, and improving the yield. From the viewpoint of handling and the like, ammonia is preferably added in the form of aqueous ammonia.
The reduction reaction is carried out using a reducing agent. Examples of the reducing agent include hydrazine and hydrazine monohydrate. When a phosphorus-based reducing agent such as hypophosphorous acid or a reducing agent other than hydrazine such as a boron-based reducing agent such as dimethylaminoborane is used, nanowires may not be obtained.
In the case of using hydrazine monohydrate as the reducing agent, the concentration thereof is preferably 1 to 20mol, more preferably 2 to 10mol, further preferably 2 to 4mol, and particularly preferably 2.5 to 3.5mol, based on 1mol of the total of the iron salt and the nickel salt, from the viewpoints of reducing reactivity of iron ions and nickel ions, controlling the shape of the obtained nanowire, and improving the yield. The order of adding the nickel salt, iron salt, citrate, ammonia, reducing agent, and the like during the reduction reaction is not particularly limited as long as the reducing agent is added last.
Upon reduction reaction, nanowires can be obtained by applying a magnetic field. The magnetic field may be applied by a magnetic circuit made of a rubidium magnet, and the intensity is preferably about 100mT, and particularly preferably 100 to 200 mT.
The temperature and reaction time of the reduction reaction are not particularly limited as long as the reduction reaction proceeds. For example, in the case of using hydrazine such as hydrazine or hydrazine monohydrate as the reducing agent, the temperature of the reduction reaction is preferably 70 to 100 ℃, more preferably 80 to 100 ℃, and further preferably 80 to 95 ℃ from the viewpoints of the reduction reactivity of iron ions and nickel ions, the shape control of the nanowires, and the improvement of the yield. In addition, the reduction time is preferably 30 minutes or more, and more preferably 60 minutes or more, from the viewpoints of reduction reactivity of iron ions and nickel ions, shape control of nanowires, and improvement of yield.
After the reduction reaction, the nanowire dispersion can be purified and recovered by filtration, decantation, or the like, and preferably, the nanowire dispersion can be purified and recovered by filtration. Examples of the filtration method include suction filtration and pressure filtration.
The filter used for filtration is not particularly limited as long as it can use an alkaline solvent or a polar solvent. Even if the filter is a hydrophobic filter such as polyvinylidene fluoride resin (PVDF), the filter can be used if the filter surface is wetted with alcohol or the like. The pore size of the filter is not particularly limited as long as it is smaller than the nanowire length, and specifically, is preferably 10 μm or less.
The electromagnetic wave shielding material of the present invention can be obtained by further mixing a dielectric material into the purified and recovered nanowires. Specifically, the electromagnetic wave shielding material of the present invention contains nanowires dispersed in a dielectric. Examples of the dielectric include compounds other than compounds of the conductor and the semiconductor, and examples thereof include organic materials such as epoxy resins, acrylic resins, styrene resins, polyester resins, alkyd resins, phenol resins, urethane resins, polyamide resins, polyimide resins, silicone resins, fluorine resins, elastomers, and rubbers (particularly natural rubbers); and inorganic materials such as ceramics. The dielectric also has the effect of acting as a binder. By mixing a dielectric material into the nanowire, molding becomes possible, and an electromagnetic wave shield can be manufactured. Among these, epoxy resins, silicone resins, fluororesins, ceramics, and the like are preferable because they have excellent heat resistance and low moisture absorption, and further, epoxy resins, silicone resins, and electronic components have excellent adhesion. From the viewpoint of further improving the electromagnetic wave shielding property (particularly, electromagnetic wave absorption property) of the electromagnetic wave shielding material, the dielectric is preferably a styrene resin, a silicone resin, or an epoxy resin, more preferably a styrene resin or a silicone resin, and still more preferably a styrene resin. The resin is used in a concept including a polymer.
The mass ratio of the nanowire to the dielectric (nanowire/dielectric) of the electromagnetic wave shielding material of the present invention is not particularly limited, but is usually 10/90 to 95/10, and is preferably 10/90 to 90/10, more preferably 10/90 or more and less than 65/35, and further preferably 40/60 to 60/40, from the viewpoint of further improving the electromagnetic wave shielding property (particularly, electromagnetic wave absorption property). The mass ratio can be appropriately changed by shielding electromagnetic waves by reflection or absorption.
When the ratio of the nanowire to the total of the nanowire and the dielectric is 10 mass% or more and less than 65 mass%, a dielectric material can be obtained. Specifically, the volume resistivity of the obtained material can be set to 10－2Omega cm or more (especially 4.4X 10)6Ω · cm or more). Such materials may be shielded primarily by absorption of electromagnetic waves. Generally, the higher the ratio of nanowires is within the allowable range, the higher the performance relating to electromagnetic wave shielding properties (particularly electromagnetic wave absorption properties), but the workability is deteriorated, and there is a possibility that the working means is limited to pouring, dipping, screen printing, and the like, and if the ratio of nanowires is lowered, various kinds of coating such as die coater and spray coating, transfer, press molding, and the like become possible. From the viewpoint of the balance between electromagnetic wave shielding properties (particularly, electromagnetic wave absorption properties) and processability, the proportion of the nanowire is preferably 40 to 60% by mass relative to the total of the nanowire and the dielectric.
When the ratio of the nanowire to the total of the nanowire and the dielectric is 65 to 90 mass%, a conductor can be obtained. Specifically, the volume resistivity of the resulting material can be made to be less than 10－2Omega cm. The ratio of the nanowire to the total of the nanowire and the dielectric is more preferably 80 to 90 mass%. Such materials may be shielded primarily by reflecting electromagnetic waves.
The electromagnetic wave shielding material of the present invention may contain a filler, a softening agent, an antioxidant, a thickener, and the like, within a range not to impair the effects of the present invention. The electromagnetic wave shielding material of the present invention may be cured (or crosslinked) using a curing agent (or crosslinking agent).
The electromagnetic wave shielding material of the present invention can be manufactured by mixing iron-nickel nanowires with a dielectric. The mixing method is not particularly limited, and for example, a method of mixing the components using a solvent or the like by a planetary mixer to prepare a dispersion liquid containing the electromagnetic wave shielding material and molding the dispersion liquid is exemplified.
Specifically, for example, when the dielectric is an organic material, the electromagnetic shielding material of the present invention can be obtained by dispersing iron-nickel nanowires in a solvent containing the organic material to prepare a dispersion, applying the dispersion, and drying the solvent. The organic material may be dissolved in the dispersion liquid, or the organic material may be dispersed. As the organic material, a monomer (particularly, a polymerizable monomer) that can form the organic material may be used, and in this case, it is sufficient if polymerization (or curing) is performed after the dispersion liquid is applied. In this case, the dispersion may contain no solvent. The dispersion may also be used in the form of a paste. The sheet can be obtained by filling the above dispersion or paste into a plate-like template and curing the same.
In addition, for example, when the dielectric is an organic material, the electromagnetic shielding material of the present invention can be obtained by melting and mixing the organic material and the iron-nickel nanowires and molding them.
In addition, for example, in the case where the dielectric is an inorganic material, the electromagnetic wave shielding material of the present invention can be obtained by mixing the inorganic material and the iron-nickel nanowires together with a solvent and molding and sintering the mixture.
The present invention also provides a dispersion liquid containing the electromagnetic wave shielding material. The dispersion liquid containing the electromagnetic wave shielding material means a dispersion liquid capable of producing the electromagnetic wave shielding material of the present invention. The dispersion liquid contains the iron-nickel nanowires constituting the electromagnetic wave shielding material of the present invention and a solvent and, depending on the desired dielectric (e.g., an organic material or a monomer (particularly, a polymerizable monomer) that can form the organic material). As the solvent, any solvent used in the field of dispersion of nanowires can be used, and examples thereof include organic solvents such as toluene, xylene, and methyl ethyl ketone. When a monomer (particularly, a polymerizable monomer) capable of forming the organic material is used as the organic material, the dispersion may contain no solvent.
The shape of the electromagnetic shielding material of the present invention is not particularly limited, and examples thereof include a sheet, a film and the like. The electromagnetic shielding material of the present invention can also be used as a coating film for various electronic components such as semiconductors. The sheet and the film may have a thickness of 1 μm to 5 mm. The coating film may have a thickness of 1 to 500 μm.
The electromagnetic wave shielding material of the present invention (particularly, the electromagnetic wave shielding material of the present invention in which the ratio of the nanowires to the total of the nanowires and the dielectric is 10 mass% or more and less than 65 mass%) can absorb electromagnetic waves (radio waves) even at a frequency of 18GHz or more. Specifically, the electromagnetic wave having a frequency of 18GHz or more preferably has an absorption of 15dB or more on average in any of the following frequency regions, and more preferably a plurality of frequency bands of 3 bands or more can be absorbed in these regions. Further, as the absorptance, it is more preferable that the absorptance is 15dB or more because 97% of the radio wave power can be absorbed, and it is more preferable that the absorptance is 20dB because 99% of the radio wave power can be absorbed.
(frequency region)
N257 (26.50-29.50 GHz) used in Japan and Korea, n258 (24.25-27.50 GHz) used in EU, n259 (39.5-43.50 GHz), n260 (37.00-40.00 GHz), and n261 (27.50-28.35 GHz) used in the United states and China in the 5 th-generation mobile communication system; and
in the millimeter wave radar as a part of the advanced driving assistance system, 24.05 to 24.25GHz as a 24GHz band narrow band radar system, 24.25 to 29.0GHz as a 24GHz/26GHz band UWB radar system, 60.0 to 61.0GHz as a 60GHz band millimeter wave radar system, 76.0 to 77.0GHz as a 76GHz band millimeter wave radar system, and 77.0 to 81.0GHz as a 79GHz band high resolution radar system.
The electromagnetic wave shielding property of the member using the electromagnetic wave shielding material of the present invention may be designed to have an absorption rate and a shielding rate suitable for the application. The shielding rate is 10dB, 90% of the electric power of electromagnetic waves can be shielded, 15dB, 20dB, 25dB, 99.7% and 30dB, and 99.9% of the electric power can be shielded.
The electromagnetic wave shielding material of the present invention can exhibit an absorption of 15dB or more on average, particularly 20dB or more, in the following frequency bands by setting the ratio of the nanowire to 40 to 60 mass% with respect to the total of the nanowire and the dielectric:
·n257(26.50－29.50GHz)；
n261 (27.50-28.35 GHz); and
77.0-81.0 GHz as a 79GHz band high resolution radar system.
The electromagnetic wave absorbability and the electromagnetic wave shielding property of the sheet of the present invention can be changed by treatment in a magnetic field. For example, by remelting the electromagnetic shielding material of the present invention in a magnetic field and molding it, the absorptance in a frequency band with low absorptance can be improved.
In one embodiment of the present invention, the electromagnetic wave shielding material of the present invention has an absorption property for electromagnetic waves at a frequency of 18GHz or more. In detail, the following is described.
The electromagnetic wave shielding material can absorb electromagnetic waves with the frequency of 26.5-29.5 GHz which is more than 10dB on average.
The electromagnetic wave shielding material can absorb electromagnetic waves with the frequency of 24.5-27.5 GHz which is more than 10dB on average.
The electromagnetic wave shielding material can absorb electromagnetic waves with the frequency of 39.5-43.5 GHz which is more than 10dB on average.
The electromagnetic wave shielding material can absorb electromagnetic waves with the frequency of 37.0-40.0 GHz which is more than 10dB on average.
The electromagnetic wave shielding material can absorb electromagnetic waves with the frequency of 27.5-28.35 GHz which is more than 10dB on average.
The electromagnetic wave shielding material can absorb electromagnetic waves with the frequency of 24.05-24.25 GHz which is more than 10dB on average.
The electromagnetic wave shielding material can absorb electromagnetic waves with the frequency of 24.25-29.0 GHz which is more than 10dB on average.
The electromagnetic wave shielding material can absorb electromagnetic waves with the frequency of 60.0-61.0 GHz which is more than 10dB on average.
The electromagnetic wave shielding material can absorb electromagnetic waves with the frequency of 76.0-77.0 Hz of more than 10dB on average.
The electromagnetic wave shielding material can absorb electromagnetic waves with frequencies of 77.0-81.0 GHz and above 10dB on average.
In another embodiment of the present invention, the electromagnetic wave shielding material of the present invention can have an average value of electromagnetic wave absorbability at frequencies of 18 to 110GHz of 10dB or more when processed into a sheet having a thickness of 1mm, and the electromagnetic wave shielding material of the present invention can have a maximum peak at any frequency of 18 to 110GHz and a maximum value of the maximum peak can be 50dB or more. Further, the electromagnetic wave shielding material of the present invention can have an average value of electromagnetic wave shielding properties at a frequency of 18 to 110GHz of 10dB or more when processed into a sheet having a thickness of 1 mm. In the present invention, the reason is not clear, but it is presumed that specific electromagnetic wave shielding properties are exhibited by using nanowires made of iron and nickel having high magnetic permeability.
In still another embodiment of the present invention, when the electromagnetic wave shielding material of the present invention is used as an electromagnetic wave absorber against noise or the like, the maximum value of the electromagnetic wave absorbability is preferably 20dB or more, and more preferably 40dB or more at a frequency of 18GHz or more.
Examples
The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.
The evaluation was performed by the following method.
A. Evaluation of electromagnetic wave shielding Material
(1) Volume resistivity
The sheets obtained in examples and comparative examples were measured for 5 sites in accordance with JIS K7194 (1994), and the average value was calculated.
(2) Absorption of electromagnetic waves
Electromagnetic wave absorption measurements were performed in a free space method using a vector network analyzer for a K band (18 to 26.5GHz), a Ka band (26.5 to 40GHz), a U band (40 to 60GHz), an E band (60 to 90GHz), and a W band (75 to 110GHz) using sheets obtained in examples and comparative examples, to which aluminum plates were attached, as samples.
For example, the results of the measurement of the electromagnetic wave absorption in the K band, Ka band, U band, and E band of the sheet of example 1 are shown in fig. 1 to 4, respectively.
Further, for example, the results of the measurement of the electromagnetic wave absorption in the K band, Ka band, U band, and E band of the sheet of example 5 are shown in fig. 9 to 12, respectively.
Fig. 17 to 20 show the results of the measurement of the electromagnetic wave absorption in the K band, Ka band, U band, and E band of the sheet of comparative example 2, for example.
As evaluation of the measurement results, average values of absorptances of 10 frequency bands in a range of n257 (26.50-29.50 GHz), n258 (24.25-27.50 GHz), n259 (39.5-43.50 GHz), n260 (37.00-40.00 GHz), n261 (27.50-28.35 GHz), 24GHz band narrow band radar system (24.05-24.25 GHz), 24GHz/26GHz band UWB radar system (24.25-29.0 GHz), 60GHz band millimeter wave radar system (60.0-61.0 GHz), 76GHz band millimeter wave radar system (76.0-77.0 GHz), and 79GHz band high resolution radar system (77.0-81.0 GHz) were calculated. The respective average values were evaluated according to the contents of the metal components by the following criteria. In the present invention, the more preferable the band is good or excellent at any content.
The samples containing 50 mass% of metal components were evaluated for each average value according to the following criteria, and subjected to comprehensive evaluation.
(average value of absorptance in each frequency band)
Very good: more than 20 dB;
good: more than 15dB and less than 20 dB;
and (delta): more than 10dB and less than 15 dB;
x: less than 10 dB.
(comprehensive evaluation of absorptivity in each frequency band)
Optimally: the number of frequency bands of excellent and good is 7 or more;
and (3) excellent: the number of frequency bands of excellent and good is 6;
good: the number of frequency bands of excellent and good is 5;
can be as follows: the number of good and good frequency bands is 3-4;
not: the number of frequency bands excellent and good is 2 or less.
In the present invention, when the metal component is contained at 50 mass%, the "comprehensive evaluation of absorptance in each frequency band" is required to be at a level of "ok" or more, preferably at a level of "good" or more, more preferably at a level of "excellent" or more, and most preferably at a level of "optimum".
The samples containing 20 mass% of the metal component were evaluated for each average value according to the following criteria, and subjected to comprehensive evaluation.
(average value of absorptance in each frequency band)
Good: more than 10 dB;
x: less than 10 dB.
(comprehensive evaluation of absorptivity in each frequency band)
And (3) excellent: the number of good frequency bands is 3 or more;
good: the number of frequency bands of good is 2;
can be as follows: the number of frequency bands of good is 1;
not: the number of frequency bands of good is 0.
In the present invention, when the metal component is contained at 20 mass%, the "comprehensive evaluation of absorptance in each frequency band" is required to be at a level of "ok" or more, preferably at a level of "good" or more, and more preferably "excellent".
For the samples containing 10 mass% of the metal component, the respective average values were evaluated according to the following criteria, and the overall evaluation was performed.
(average value of absorptance in each frequency band)
Good: more than 10 dB;
x: less than 10 dB.
(comprehensive evaluation of absorptivity in each frequency band)
Can be as follows: the number of good frequency bands is 1 or more;
not: the number of frequency bands of good is 0.
In the present invention, when the metal component is contained in an amount of 10 mass%, the "comprehensive evaluation of absorptance in each frequency band" is required to be at a level of not less than "acceptable".
Next, the average value and the maximum value of the absorptance in the entire frequency band of 18 to 110GHz and the position (frequency) thereof were obtained, and the evaluation was performed by the following criteria.
(average value of absorptivity at 18 to 110GHz band)
Very good: more than 20 dB;
o: more than 10dB and less than 20 dB;
and (delta): 7.5dB or more and less than 10 dB;
x: less than 7.5 dB.
The average value is practically required to be 7.5dB or more, preferably 10dB or more (. largecircle. or. circleincircle.), and more preferably 20dB or more (. circleircle.).
(maximum value of absorption Rate of 18 to 110GHz)
Very good: over 40 dB;
o: more than 20dB and less than 40 dB;
and (delta): more than 10dB and less than 20 dB;
x: less than 10 dB.
In the present invention, when the maximum value of the electromagnetic wave absorbability is 10dB or more (Δ), it is determined that the maximum value is acceptable. The maximum value of the electromagnetic wave absorbability is preferably 20dB or more (°), and more preferably 40dB or more (excellent).
(3) Electromagnetic wave shielding property
Electromagnetic wave shield measurement of the K band (18 to 26.5GHz), Ka band (26.5 to 40GHz), U band (40 to 60GHz), E band (60 to 90GHz), and W band (75 to 110GHz) was performed by a free space method using the sheets obtained in examples and comparative examples as samples using a vector network analyzer.
For example, the results of the measurement of the electromagnetic shielding in the K band, Ka band, U band, and E band of the sheet of example 1 are shown in fig. 5 to 8, respectively.
Fig. 13 to 16 show the results of the measurement of the electromagnetic shielding in the K band, Ka band, U band, and E band of the sheet of example 5, for example.
Fig. 21 to 24 show the results of the measurement of the electromagnetic shielding in the K band, Ka band, U band, and E band of the sheet of comparative example 2, for example.
As evaluation of the measurement results, the average value of the shielding rates of 10 frequency bands of n257 (26.50-29.50 GHz), n258 (24.25-27.50 GHz), n259 (39.5-43.50 GHz), n260 (37.00-40.00 GHz), n261 (27.50-28.35 GHz), 24GHz band narrow band radar system (24.05-24.25 GHz), 24GHz/26GHz band UWB radar system (24.25-29.0 GHz), 60GHz band millimeter wave radar system (60.0-61.0 GHz), 76GHz band millimeter wave radar system (76.0-77.0 GHz), and 79GHz band high resolution radar system (77.0-81.0 GHz) was calculated. The respective average values were evaluated according to the contents of the metal components by the following criteria. In the present invention, the more preferable the band is good or excellent at any content.
The samples containing 50 mass% of metal components were evaluated for each average value according to the following criteria, and subjected to comprehensive evaluation.
(average value of shielding rates of respective frequency bands)
Very good: more than 20 dB;
good: more than 15dB and less than 20 dB;
and (delta): more than 10dB and less than 15 dB;
x: less than 10 dB.
(comprehensive evaluation of Shielding Rate in each frequency band)
Optimally: the number of the frequency bands is 10;
and (3) excellent: the number of the frequency bands is 9;
good: the number of the frequency bands is 8;
can be as follows: the number of the frequency bands is 7;
not: the number of the frequency bands is 6 or less.
In the present invention, when the metal component is contained at 50 mass%, the "comprehensive evaluation of the shielding rate in each frequency band" is required to be at a level of "ok" or more, preferably at a level of "good" or more, more preferably at a level of "excellent" or more, and most preferably at a level of "optimal".
The samples containing 20 mass% of the metal component were evaluated for each average value according to the following criteria, and subjected to comprehensive evaluation.
(average value of shielding rates of respective frequency bands)
Good: more than 10 dB;
x: less than 10 dB.
(comprehensive evaluation of Shielding Rate in each frequency band)
And (3) excellent: the number of good frequency bands is 9 or more;
good: the number of frequency bands of good component is 8;
can be as follows: the number of frequency bands of good is 7;
not: the number of frequency bands of good is 6 or less.
In the present invention, when the metal component is contained at 20 mass%, the "comprehensive evaluation of the shielding rate in each frequency band" is required to be at a level of "ok" or more, preferably at a level of "good" or more, and more preferably "excellent".
The samples containing 10 mass% of the metal component were evaluated for each average value according to the following criteria, and subjected to comprehensive evaluation.
(average value of shielding rates of respective frequency bands)
Good: more than 10 dB;
x: less than 10 dB.
(comprehensive evaluation of Shielding Rate in each frequency band)
Optimally: the number of good frequency bands is 5 or more;
and (3) excellent: the number of frequency bands of good is 3 or 4;
good: the number of frequency bands of good is 2;
can be as follows: the number of frequency bands of good component 1;
not: the number of frequency bands of good is 0.
In the present invention, when the metal component is contained in an amount of 10 mass%, the "comprehensive evaluation of the shielding rate in each frequency band" is required to be at a level of not less than "acceptable".
Next, the average value of the shielding rates of the 28GHz band (frequency band of 1GHz width centered at 28 GHz), the average value of the shielding rates of the 79GHz band (frequency band of 1GHz width centered at 79 GHz), and the average value and the maximum value of the shielding rates of the entire frequency bands of 18 to 110GHz were obtained, and the evaluation was performed according to the criteria below.
(average value of shielding rates at 28GHz band, 79GHz band and 18-110 GHz)
Very good: more than 25 dB;
o: more than 20dB and less than 25 dB;
and (delta): more than 10dB and less than 20 dB;
x: less than 10 dB.
The average value is practically required to be 10dB or more, preferably 20dB or more (. largecircle. or. circleincircle.), and more preferably 25dB or more (. circleircle.).
(maximum value of shielding Rate 18 to 110GHz)
Very good: over 70 dB;
o: more than 20dB and less than 70 dB;
and (delta): more than 10dB and less than 20 dB;
x: less than 10 dB.
In the present invention, when the maximum value of the electromagnetic wave shielding property is 10dB or more (Δ), it is determined that the electromagnetic wave shielding property is acceptable. The maximum value of the electromagnetic wave shielding property is preferably 20dB or more (°), and more preferably 70dB or more (excellent).
B. Material
The nanowires and particles used in the electromagnetic wave shielding material of the present invention are produced as follows.
(1) Nanowires of iron and nickel (FeNiNW1, Fe: Ni ═ 21.5: 78.5)
15.35g (64.58mmol) of nickel chloride hexahydrate and 0.30g (1.02mmol) of trisodium citrate dihydrate were added to ethylene glycol to make 350.0g of the total amount. The solution was heated to 90 ℃ to dissolve the nickel chloride, resulting in a nickel-citrate solution.
2.50g (62.52mmol) of sodium hydroxide was added to ethylene glycol to obtain 388.5g in total. The solution was heated to 90 ℃ to dissolve sodium hydroxide, yielding a sodium hydroxide solution.
3.70g (18.61mmol) of iron (II) chloride tetrahydrate was added to ethylene glycol to make 150.0g in total. Iron (II) chloride tetrahydrate was dissolved by stirring at room temperature to obtain an iron solution.
A reaction vessel in a magnetic circuit capable of applying a magnetic field to the center was heated to 90 to 95 ℃ and 350.0g of a nickel-citrate solution, 388.5g of a sodium hydroxide solution, 100.0g of 28% aqueous ammonia (28.0 g of ammonia), 150.0g of an iron solution, and 11.5g (229.72mmol) of hydrazine monohydrate were added in this order. After all the addition, a magnetic field of 150mT was applied to conduct reduction reaction at 90-95 ℃ for 90 minutes.
After the reaction was completed, the nanowires were recovered using a PTFE filter of T100a 090C.
The recovered nanowires were confirmed by ICP-MS, and the mass ratio of iron to nickel was 21.5/78.5. The average values of the length, diameter and aspect ratio of the nanowires were 22.6 μm, 0.2 μm and 113, respectively.
(2) Nanowires of iron and nickel (FeNiNW2, Fe: Ni 55: 45)
8.18g (34.43mmol) of nickel chloride hexahydrate and 0.30g (1.02mmol) of trisodium citrate dihydrate were added to ethylene glycol to make 350.0g of the total amount. The solution was heated to 90 ℃ to dissolve the nickel chloride, resulting in a nickel-citrate solution.
2.50g (62.52mmol) of sodium hydroxide was added to ethylene glycol to obtain 388.5g in total. The solution was heated to 90 ℃ to dissolve sodium hydroxide, yielding a sodium hydroxide solution.
9.24g (46.48mmol) of iron (II) chloride tetrahydrate was added to ethylene glycol to make 150.0g in total. Iron (II) chloride tetrahydrate was dissolved by stirring at room temperature to obtain an iron solution.
A reaction vessel in a magnetic circuit capable of applying a magnetic field to the center was heated to 90 to 95 ℃ and 350.0g of a nickel-citrate solution, 388.5g of a sodium hydroxide solution, 100.0g of 28% aqueous ammonia (28.0 g of ammonia), 150.0g of an iron solution, and 11.5g (229.72mmol) of hydrazine monohydrate were added in this order. After all the addition, a magnetic field of 150mT was applied to conduct reduction reaction at 90-95 ℃ for 90 minutes.
After the reaction was completed, the nanowires were recovered using a PTFE filter of T100a 090C.
The recovered nanowires were confirmed by ICP-MS, and the mass ratio of iron to nickel was 54.8/45.2. The average values of the length, diameter and aspect ratio of the nanowires were 24.6 μm, 0.2 μm and 123, respectively.
(3) Nanowires of iron and nickel (FeNiNW3, Fe: Ni ═ 64: 36)
6.89g (28.99mmol) of nickel chloride hexahydrate and 0.30g (1.02mmol) of trisodium citrate dihydrate were added to ethylene glycol to give 350.0g in total. The solution was heated to 90 ℃ to dissolve the nickel chloride, resulting in a nickel-citrate solution.
2.50g (62.52mmol) of sodium hydroxide was added to ethylene glycol to obtain 388.5g in total. The solution was heated to 90 ℃ to dissolve sodium hydroxide, yielding a sodium hydroxide solution.
10.78g (54.17mmol) of iron (II) chloride tetrahydrate was added to ethylene glycol to make 150.0g in total. Iron (II) chloride tetrahydrate was dissolved by stirring at room temperature to obtain an iron solution.
A reaction vessel in a magnetic circuit capable of applying a magnetic field to the center was heated to 90 to 95 ℃ and 350.0g of a nickel-citrate solution, 388.5g of a sodium hydroxide solution, 100.0g of 28% aqueous ammonia (28.0 g of ammonia), 150.0g of an iron solution, and 11.5g (229.72mmol) of hydrazine monohydrate were added in this order. After all the addition, a magnetic field of 150mT was applied to conduct reduction reaction at 90-95 ℃ for 90 minutes.
After the reaction was completed, the nanowires were recovered using a PTFE filter of T100a 090C.
The recovered nanowires were confirmed by ICP-MS, and the mass ratio of iron to nickel was 64.0/36.0. The average values of the length, diameter and aspect ratio of the nanowires were 23.2 μm, 0.2 μm and 116, respectively.
(4) Particles made of iron and nickel (FeNiP)
15.35g (64.58mmol) of nickel chloride hexahydrate and 0.30g (1.02mmol) of trisodium citrate dihydrate were added to ethylene glycol to make 350.0g of the total amount. The solution was heated to 90 ℃ to dissolve the nickel chloride, resulting in a nickel-citrate solution.
2.50g (62.52mmol) of sodium hydroxide was added to ethylene glycol to obtain 388.5g in total. The solution was heated to 90 ℃ to dissolve sodium hydroxide, yielding a sodium hydroxide solution.
3.70g (18.61mmol) of iron (II) chloride tetrahydrate was added to ethylene glycol to make 150.0g in total. Iron (II) chloride tetrahydrate was dissolved by stirring at room temperature to obtain an iron solution.
The reaction vessel was heated to 90 to 95 ℃ and 350.0g of a nickel-citrate solution, 388.5g of a sodium hydroxide solution, 100.0g (28.0 g of ammonia), 150.0g of an iron solution and 11.5g (229.72mmol) of hydrazine monohydrate were added in this order. After all the components were added, the reaction was reduced at 90 to 95 ℃ for 90 minutes.
After the reaction was completed, the nanowires were recovered using a PTFE filter of T100a 090C.
The recovered particles were confirmed by ICP-MS, and the mass ratio of iron to nickel was 21.5/78.5. Since the particles are in the form of particles, the aspect ratio is 1.
(5) Nanowires made of nickel (NiNW)
4.00g (16.8mmol) of nickel chloride hexahydrate, 0.375g (1.27mmol) of trisodium citrate dihydrate were added to ethylene glycol to make 500.0g in total. The solution was heated to 90 ℃ to dissolve it, yielding a nickel-citrate solution.
In another vessel, 1.00g of sodium hydroxide was added to ethylene glycol in a total amount of 499.0 g. The solution was heated to 90 ℃ to dissolve it, yielding a sodium hydroxide solution.
A reaction vessel in a magnetic circuit capable of applying a magnetic field to the center was heated to 90 to 95 ℃ and then 500.0g of a nickel-citrate solution, 499.0g of a sodium hydroxide solution, and 1.0g (229.72mmol) of hydrazine monohydrate were added in this order. After all the addition, a magnetic field of 150mT was applied to conduct reduction reaction at 90-95 ℃ for 90 minutes.
After the reaction was completed, the nanowires were recovered using a PTFE filter of T100a 090C. The average values of the length, diameter and aspect ratio of the nanowires were 24 μm, 0.1 μm and 240, respectively.
Example 1
The FeNiNW 110g, 10g of a styrene resin (St, manufactured by fuji film & mitsubishi) and 10g of toluene were mixed with a planetary mixer to obtain a dispersion.
The obtained dispersion was cast on a Teflon sheet, dried at 40 ℃ and the coating film was peeled off from the Teflon sheet to obtain a sheet having a thickness of 1 mm.
Example 2
9g of FeniNW 110g and TSE3450(Si, silicone resin manufactured by MOMENTIVE corporation) were mixed by a planetary mixer, and 1g of TSE3450 (curing agent for silicone resin manufactured by MOMENTIVE corporation) was further mixed to obtain a dispersion.
The obtained dispersion was cast on a polycarbonate resin sheet, cured at room temperature for 24 hours or more, and the film was peeled from the polycarbonate resin sheet to obtain a sheet having a thickness of 1 mm.
Examples 3 and 4
A sheet was obtained in the same manner as in example 1 except that the mass ratio of the FeNiNW1 to the styrene resin was changed to the mass ratio of the FeNiNW and the styrene resin used in table 2A or 3A.
Example 5
A teflon sheet was laminated on both sides of the sheet produced in example 1, and a laminated body composed of the teflon sheet/the sheet obtained in example 1/the teflon sheet was produced.
After the thickness of the end of the obtained laminate was fixed by a spacer plate having a thickness of 1mm, the laminate was sandwiched between 2 ferrite magnet plates and heat-treated at 130 ℃ for 4 hours. Thereafter, the laminate was taken out, and the Teflon sheet was peeled off to obtain a sheet having a thickness of 1 mm.
Example 6
The FeNiNW 113 g and 9g of jER (Ep, epoxy resin manufactured by mitsubishi chemical corporation) were mixed by a planetary mixer, and 4g of trimethylhexamethylenediamine was further mixed to obtain a dispersion.
The obtained dispersion was cast on a Teflon sheet, cured at 120 ℃ for 30 minutes or more, and the coating film was peeled off from the Teflon sheet to obtain a sheet having a thickness of 1 mm.
Examples 7 and 8
A sheet having a thickness of 1mm was obtained in the same manner as in example 6, except that the FeNiNW1 was changed to FeNiNW2 or FeNiNW 3.
Comparative example 1
A sheet was obtained in the same manner as in example 1, except that the FeNiNW was changed to FeNiP.
Comparative example 2
A sheet was obtained in the same manner as in example 1, except that the FeNiNW was changed to the ninnw.
Comparative example 3
A sheet was obtained in the same manner as in example 2, except that the FeNiNW was changed to the ninnw.
Comparative example 4
A sheet was obtained in the same manner as in example 3, except that the FeNiNW was changed to the ninnw.
Comparative example 5
A sheet was obtained in the same manner as in example 4, except that the FeNiNW was changed to the ninnw.
Comparative example 6
A sheet was obtained in the same manner as in example 1, except that the FeNiNW was changed to AgNW (manufactured by Aldrich).
The compositions and evaluation results of the electromagnetic wave shielding materials obtained in examples and comparative examples are shown in tables 1A, 1B, 1C, 2A, 2B, 2C, 3A, 3B, 3C, 4A, 4B, and 4C.
[ Table 1A ]
[ Table 1B ]
[ Table 1C ]
[ Table 2A ]
The metal content was 20 mass%
[ Table 2B ]
-: and (4) not measuring.
[ Table 2C ]
-: and (4) not measuring.
[ Table 3A ]
The content of the metal component was 10% by mass
[ Table 3B ]
-: and (4) not measuring.
[ Table 3C ]
-: and (4) not measuring.
[ Table 4A ]
The content of the metal component was 50 mass%
[ Table 4B ]
-: and (4) not measuring.
[ Table 4C ]
-: and (4) not measuring.
Examples 1, 2 and 6 containing 50% of the metal component had an absorption rate of an electromagnetic wave of 15dB or more in 6 or more frequency bands among 10 frequency bands used, and all had excellent electromagnetic wave shielding properties. On the other hand, in comparative examples 1 to 3 and 6, since the content of the metal component was the same as in examples 1, 2 and 6 and the nanowires composed of iron and nickel were not included, the number of bands which can absorb 15dB or more was less than 3 (particularly 2 or less), and the frequency band which cannot be sufficiently absorbed was large, and the use of the material was limited.
Example 3 containing 20% of the metal component absorbed 4 of the frequency band of 10dB or more, and was excellent in electromagnetic wave shielding properties. Comparative example 4, which is a comparative example, cannot absorb a frequency band of 10dB or more.
The example 4 containing 10% of the metal component can absorb only one frequency band of 10dB or more, but the comparative example 5 cannot absorb the frequency band of 10dB or more.
In example 5, the same composition as in example 1 was used, but the n258(24.25 to 27.5GHz) and 24GHz narrowband radar systems (24.05 to 24.25GHz) and 24GHz/26GHz UWB radar systems (24.25 to 29.0GHz) having absorbances of less than 15dB, which were not absorbed in example 1, were melt-reshaped in a magnetic field, and high absorbances of 20dB or more were confirmed.
Industrial applicability
The electromagnetic wave shielding material of the present invention is excellent in electromagnetic wave shielding properties, particularly electromagnetic wave absorption properties, in a high frequency region (particularly, a quasi-millimeter wave region and a millimeter wave region), and therefore can be suitably used for electronic components such as a 5 th generation mobile communication system and an advanced driving assistance system.
Claims (11)
1. An electromagnetic wave shielding material includes nanowires composed of iron and nickel.
2. The electromagnetic wave shielding material of claim 1, wherein the nanowires have a mass ratio of iron to nickel (Fe/Ni) of 20/80 to 65/35.
3. The electromagnetic wave shielding material according to claim 1 or 2, further comprising a dielectric.
4. The electromagnetic wave shielding material according to claim 3, wherein the dielectric is an adhesive.
5. The electromagnetic wave shielding material according to claim 3 or 4, wherein the proportion of the nanowire is 10% by mass or more and less than 65% by mass with respect to the total of the nanowire and the dielectric.
6. The electromagnetic wave shielding material according to claim 3 or 4, wherein the ratio of the nanowire to the total of the nanowire and the dielectric is 40 to 60% by mass.
7. The electromagnetic wave shielding material according to any one of claims 1 to 6, wherein the volume resistivity is 10－2Omega cm or more.
8. An electromagnetic wave shielding material according to any one of claims 1 to 7.
9. An electromagnetic wave shielding material comprising the electromagnetic wave shielding material according to any one of claims 1 to 7.
10. An electromagnetic wave shielding material comprising the electromagnetic wave shielding material according to any one of claims 1 to 7.
11. An electronic component comprising the electromagnetic wave shielding material according to any one of claims 1 to 7.
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| JP2019215451 | 2019-11-28 | ||
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| JP2020111760 | 2020-06-29 | ||
| PCT/JP2020/044350 WO2021107136A1 (en) | 2019-11-28 | 2020-11-27 | Electromagnetic wave blocking material |
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| TW202317286A (en) * | 2021-08-25 | 2023-05-01 | 日商尤尼吉可股份有限公司 | Terahertz wave-shielding material |
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| CN101851814A (en) * | 2010-05-14 | 2010-10-06 | 江苏大学 | Iron-nickel alloy/nickel ferrite magnetic composite nanofiber and preparation method thereof |
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| JP2019067998A (en) * | 2017-10-04 | 2019-04-25 | ユニチカ株式会社 | Electric field shield sheet or laminate |
| JP2019067997A (en) * | 2017-10-04 | 2019-04-25 | ユニチカ株式会社 | Electromagnetic wave shield sheet or laminate |
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| JP2007247036A (en) * | 2006-03-17 | 2007-09-27 | Osaka Univ | Iron-based nanofine wire and its production method, iron-based carbon-compounded fine wire and its production method, and wave absorber using the same |
| CN101851814A (en) * | 2010-05-14 | 2010-10-06 | 江苏大学 | Iron-nickel alloy/nickel ferrite magnetic composite nanofiber and preparation method thereof |
| CN103380081A (en) * | 2011-02-21 | 2013-10-30 | 东洋炭素株式会社 | Metal-carbon composite material and method for producing same |
| CN104250541A (en) * | 2013-06-26 | 2014-12-31 | 中国科学院金属研究所 | Method for absorbing microwaves by adopting dielectric/ferromagnetic composite material |
| WO2015163258A1 (en) * | 2014-04-21 | 2015-10-29 | ユニチカ株式会社 | Ferromagnetic metal nanowire dispersion and method for manufacturing same |
| CN105567110A (en) * | 2014-11-04 | 2016-05-11 | 日东电工株式会社 | Electroconductive adhesive cushioning material |
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| WO2021107136A1 (en) | 2021-06-03 |
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