WO2022131298A1 - 誘電体層の製造方法、樹脂組成物、及び誘電体層を含む積層体 - Google Patents
誘電体層の製造方法、樹脂組成物、及び誘電体層を含む積層体 Download PDFInfo
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- WO2022131298A1 WO2022131298A1 PCT/JP2021/046304 JP2021046304W WO2022131298A1 WO 2022131298 A1 WO2022131298 A1 WO 2022131298A1 JP 2021046304 W JP2021046304 W JP 2021046304W WO 2022131298 A1 WO2022131298 A1 WO 2022131298A1
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Images
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
- H01B3/002—Inhomogeneous material in general
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G4/00—Fixed capacitors; Processes of their manufacture
- H01G4/33—Thin- or thick-film capacitors
-
- 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
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
- B32B7/02—Physical, chemical or physicochemical properties
- B32B7/025—Electric or magnetic properties
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
- H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
- H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
- H01B3/44—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins
- H01B3/441—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins from alkenes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G4/00—Fixed capacitors; Processes of their manufacture
- H01G4/002—Details
- H01G4/018—Dielectrics
- H01G4/06—Solid dielectrics
- H01G4/14—Organic dielectrics
- H01G4/18—Organic dielectrics of synthetic material, e.g. derivatives of cellulose
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G4/00—Fixed capacitors; Processes of their manufacture
- H01G4/002—Details
- H01G4/018—Dielectrics
- H01G4/20—Dielectrics using combinations of dielectrics from more than one of groups H01G4/02 - H01G4/06
- H01G4/206—Dielectrics using combinations of dielectrics from more than one of groups H01G4/02 - H01G4/06 inorganic and synthetic material
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K9/00—Screening of apparatus or components against electric or magnetic fields
- H05K9/0073—Shielding materials
- H05K9/0081—Electromagnetic shielding materials, e.g. EMI, RFI shielding
- H05K9/0088—Electromagnetic shielding materials, e.g. EMI, RFI shielding comprising a plurality of shielding layers; combining different shielding material structure
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G4/00—Fixed capacitors; Processes of their manufacture
- H01G4/002—Details
- H01G4/018—Dielectrics
- H01G4/06—Solid dielectrics
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- H01G4/145—Organic dielectrics vapour deposited
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G4/00—Fixed capacitors; Processes of their manufacture
- H01G4/002—Details
- H01G4/018—Dielectrics
- H01G4/20—Dielectrics using combinations of dielectrics from more than one of groups H01G4/02 - H01G4/06
Definitions
- the present disclosure relates to a method for manufacturing a dielectric layer included in a reflective electromagnetic wave absorber, a resin composition used for forming the dielectric layer, and a laminate containing the dielectric layer.
- Patent Document 1 discloses a radio wave absorber having a dielectric layer between a resistance film containing ultrafine conductive fibers and a radio wave reflector.
- Patent Document 2 includes a first layer which is a dielectric layer or a magnetic material layer, and a conductive layer provided on at least one side of the first layer, and the relative permittivity of the first layer is 1 to 10. The electromagnetic wave absorber is disclosed.
- the dielectric layer of the reflective electromagnetic wave absorber is a layer for interfering the incident electromagnetic wave with the reflected electromagnetic wave.
- ⁇ indicates the wavelength of the electromagnetic wave to be reduced (unit: m)
- ⁇ r indicates the relative permittivity of the material constituting the dielectric layer
- d indicates the thickness of the dielectric layer (unit: m).
- Reflection attenuation is obtained by shifting the phase of the incident electromagnetic wave and the phase of the reflected electromagnetic wave by ⁇ .
- the dielectric layer has to be thickened. Therefore, there is still room for improvement in terms of manufacturing efficiency of the dielectric layer and space saving.
- the present disclosure provides a method for efficiently manufacturing a dielectric layer used for a reflective electromagnetic wave absorber, which can realize an excellent reflection attenuation amount.
- the present disclosure also provides a resin composition used for forming such a dielectric layer and a laminate containing the dielectric layer.
- One aspect of the present disclosure relates to a method for manufacturing a dielectric layer included in a reflective electromagnetic wave absorber.
- This production method comprises a step of preparing a resin composition containing at least one kind of dielectric compound and a resin component and having a relative permittivity of more than 10.0 at a frequency of 3.7 GHz or 90 GHz, and the resin composition. It includes a step of forming a dielectric layer having a thickness of 20 to 7000 ⁇ m.
- the relative permittivity of the first layer is set in the range of 1 to 10 in order to exhibit good electromagnetic wave absorption performance in a bandwidth of 50 to 100 GHz and a bandwidth of 2 GHz or more. It is accepted (see paragraph [0016] of Patent Document 2).
- the relative permittivity of the dielectric layer is set to a value higher than 10.0. This is based on the following technical ideas. That is, for example, considering a 76 GHz in-vehicle millimeter-wave radar that is expected to be put into practical use, the allowable value of the occupied frequency bandwidth is limited to the range of 500 MHz (Japan) to 1 GHz (foreign countries).
- sufficient absorption performance may be satisfied in this frequency band of about 1 GHz.
- the relative permittivity of the dielectric layer tends to decrease as the frequency increases. If the relative permittivity at a frequency of 3.7 GHz or 90 GHz is higher than 10.0, the dielectric layer according to the present disclosure can be used as an electromagnetic wave absorber for 5 G (28 GHz) or millimeter wave radar (76 GHz) first. It can be fully effective for the problems mentioned.
- One aspect of the present disclosure relates to a resin composition used for forming a dielectric layer included in a reflective electromagnetic wave absorber.
- This resin composition contains at least one kind of dielectric compound and a resin component, and has a relative permittivity higher than 10.0 at a frequency of 3.7 GHz or 90 GHz.
- the embodiment of the dielectric compound is, for example, powdery, and its relative permittivity is preferably higher than the relative permittivity of the resin component.
- Specific examples of the dielectric compound include metal compounds such as titanium oxide and barium titanate.
- the relative permittivity of the resin component at a frequency of 3.7 GHz or 90 GHz is preferably 2.5 to 9.5, for example.
- the resin composition itself has adhesiveness.
- the dielectric layer By forming the dielectric layer with the adhesive resin composition, the dielectric layer can be efficiently attached to the target member.
- the adhesive strength of the resin composition to the stainless 304 steel sheet is preferably 1.0 N / 25 mm or more.
- One aspect of the present disclosure relates to a laminate including a dielectric layer.
- This laminate includes a dielectric layer made of the above resin composition and an adhesive layer provided on at least one surface of the dielectric layer. According to such a configuration, the dielectric layer can be efficiently attached to the target member via the adhesive layer.
- a method for efficiently manufacturing a dielectric layer used for a reflection type electromagnetic wave absorber which can realize an excellent reflection attenuation amount. Further, according to the present disclosure, there is provided a resin composition used for forming such a dielectric layer and a laminate containing the dielectric layer.
- FIG. 1 is a cross-sectional view schematically showing a first embodiment of the laminated body according to the present disclosure.
- FIG. 2 is a cross-sectional view schematically showing a second embodiment of the laminated body according to the present disclosure.
- FIG. 1 is a cross-sectional view schematically showing a reflective electromagnetic wave absorber according to the first embodiment.
- the electromagnetic wave absorber 10 shown in this figure is in the form of a film or a sheet, and has a laminated structure including an electromagnetic wave transmitting layer 1, a dielectric layer 3, and a reflecting layer 4 in this order.
- the film-shaped electromagnetic wave absorber has, for example, a total thickness of 24 to 250 ⁇ m.
- the sheet-shaped electromagnetic wave absorber has, for example, an overall thickness of 0.25 to 7.1 mm.
- the electromagnetic wave transmitting layer 1 is a layer for allowing electromagnetic waves incident from the outside to reach the dielectric layer 3. That is, the electromagnetic wave transmitting layer 1 is a layer for impedance matching according to the environment and layer structure in which the electromagnetic wave absorber 10 is used, whereby the electromagnetic wave absorber 10 having a large reflection attenuation amount can be obtained.
- the sheet resistance of the electromagnetic wave transmitting layer 1 may be set according to the relative permittivity of the dielectric layer 3, for example, at 3.7 GHz.
- the sheet resistance of the electromagnetic wave transmitting layer 1 may be set in the range of 200 to 800 ⁇ / ⁇ , or may be set in the range of 350 to 400 ⁇ / ⁇ .
- the sheet resistance of the electromagnetic wave transmitting layer 1 may be set in the range of 200 to 800 ⁇ / ⁇ , and may be set in the range of 350 to 400 ⁇ / ⁇ . ..
- the electromagnetic wave transmitting layer 1 contains an inorganic material or an organic material having conductivity.
- the conductive inorganic material include indium tin oxide (ITO), zinc oxide (IZO), aluminum zinc oxide (AZO), carbon nanotubes, graphene, Ag, Al, Au, Pt, Pd, Cu, and Co. , Cr, In, Ag-Cu, Cu-Au, and nanoparticles containing one or more selected from the group consisting of Ni nanoparticles, or nanoparticles, and examples of the organic material having conductivity include polythiophene derivatives. , Polyacetylene derivatives, polyaniline derivatives, polypyrrole derivatives.
- the electromagnetic wave transmitting layer 1 may contain a mixture (PEDOT / PSS) of polyethylene dioxythiophene (PEDOT) and polystyrene sulfonic acid (PPS).
- PEDOT polyethylene dioxythiophene
- PPS polystyrene sulfonic acid
- the thickness (film thickness) of the electromagnetic wave transmitting layer 1 is preferably in the range of 0.1 nm to 100 nm, and preferably in the range of 1 nm to 50 nm. More preferred.
- the film thickness is 0.1 nm or more, it is easy to form a uniform film, and there is a tendency that the function as the electromagnetic wave transmitting layer 1 can be more sufficiently fulfilled.
- the film thickness is 100 nm or less, sufficient flexibility can be maintained, and it is possible to more reliably prevent cracks in the thin film due to external factors such as bending and tension after film formation. It tends to suppress heat damage and shrinkage to the substrate.
- the thickness (thickness) of the electromagnetic wave transmitting layer 1 is preferably in the range of 0.1 to 2.0 ⁇ m, preferably 0.1 to 0.4 ⁇ m. It is more preferable to keep it within the range.
- the film thickness is 0.1 ⁇ m or more, it is easy to form a uniform film, and there is a tendency that the function as the electromagnetic wave transmitting layer 1 can be more sufficiently fulfilled.
- the film thickness is 2.0 ⁇ m or less, sufficient flexibility can be maintained, and it is possible to more reliably prevent cracks in the thin film due to external factors such as bending and pulling after film formation. There is a tendency to be able to do it.
- Examples of the film forming method include a dry coating method and a wet coating method.
- Examples of the dry coating method include resistance heating, induction heating, a vacuum deposition method using an ion beam (EB), a sputtering method, and the like.
- the resistance heating method the material is placed in a ceramic crucible, a voltage is applied to the heater surrounding the crucible to pass an electric current, and the crucible is heated in a vacuum to evaporate the inorganic material from the opening and use it as a base material.
- a film is formed by adhering.
- the film formation speed is adjusted by controlling the distance between the material and the base material, the voltage applied to the heater, and the current. By controlling, the film thickness is controlled.
- the ion beam emits electrons by passing an electric current through the filament in a vacuum, and by directly hitting the material with the electrons emitted by the electromagnetic lens, it heats and evaporates the inorganic material and attaches it to the substrate to form a film. do. It is used when an inorganic material that requires a large amount of heat or a large film formation rate is required for evaporation.
- the distance between the material and the base material, the amount of electrons generated from the filament by the electric current, and the irradiation position and range (squeezing) of the material are controlled by the electromagnetic lens, the film formation speed is adjusted, and the shutter opening / closing time and line speed are used as described above.
- the film time is controlled and the film thickness is controlled.
- a rare gas such as Ar is mainly introduced onto a target made of an inorganic material, Ar is turned into plasma by applying a voltage, and the plasmaized Ar is accelerated by the voltage and collides with the target. , The material is physically blown off (sputtering) and adhered to the base material to form a film. Inorganic materials that cannot be formed by the air vapor deposition method may be able to be formed by the sputtering method.
- the film formation speed is adjusted by controlling the distance between the target and the base material, the power applied to the target, and the Ar gas pressure, and the film formation time is controlled by the shutter opening / closing time and line speed as described above to control the film thickness. do. It is mainly used when forming a film of an inorganic material.
- the wet coating method is a method in which a material is mainly applied to a base material.
- a solid material under normal temperature and pressure is appropriately dissolved in a solvent or inked by dispersion, coated, and then dried to remove the solvent to form a film. do.
- Examples of the coating method include a die coat, a micro gravure coat, a rod gravure coat, and a gravure coat.
- the rotation ratio is controlled, ink is applied to the substrate, and the substrate is dried to control the film thickness. It is mainly used when forming films of organic materials and some inorganic dispersion materials.
- the sheet resistance value of the electromagnetic wave transmitting layer 1 can be measured using, for example, Lorester GP MCP-T610 (trade name, manufactured by Mitsubishi Chemical Analytech Co., Ltd.).
- the dielectric layer 3 is a layer for interfering an incident electromagnetic wave with a reflected electromagnetic wave.
- ⁇ indicates the wavelength of the electromagnetic wave to be suppressed (unit: m)
- ⁇ r indicates the relative permittivity of the material constituting the dielectric layer 3
- d indicates the thickness of the dielectric layer 3 (unit: m). show. Reflection attenuation is obtained by shifting the phase of the incident electromagnetic wave and the phase of the reflected electromagnetic wave by ⁇ .
- the dielectric layer 3 is composed of a resin composition having a relative permittivity higher than 10.0 at a frequency of 3.7 GHz. Since the relative permittivity of the dielectric layer 3 is higher than 10.0, excellent absorption performance (preferably ⁇ 15 dB, more preferably ⁇ 20 dB) can be realized in a specific frequency band as described above. In addition to this, since the dielectric layer 3 can be made thin, both productivity improvement and space saving of the dielectric layer 3 can be achieved to a high level.
- the relative permittivity of the dielectric layer 3 at a frequency of 3.7 GHz is preferably higher than 10.0 and 30.0 or less, and more preferably higher than 10.0 and 20.0 or less.
- the dielectric layer 3 When the relative permittivity of the dielectric layer 3 at a frequency of 3.7 GHz or less is 30.0 or less, the dielectric layer 3 having sufficient strength tends to be formed. For example, if an excessive amount of a dielectric compound is added to the dielectric layer 3 in order to increase the relative permittivity of the dielectric layer 3, the dielectric layer 3 tends to become brittle.
- the thickness of the dielectric layer 3 may be appropriately set according to the frequency band and the relative permittivity. For example, assuming use in a 60 GHz, 76 GHz or 90 GHz band such as a millimeter wave radar, the thickness of the dielectric layer 3 is preferably 100 to 400 ⁇ m, more preferably 250 to 400 ⁇ m.
- the thickness of the dielectric layer 3 is preferably 450 to 7000 ⁇ m, more preferably 650 to 6500 ⁇ m. Further, the thickness of the dielectric layer 3 is preferable when it is assumed that the terahertz wave, for example, 300 GHz or 350 GHz band, which has been attracting attention in the fields of next-generation communication standards, measurement / analysis technology, medical treatment, etc., is used in recent years. Is 20 to 80 ⁇ m, more preferably 50 to 80 ⁇ m.
- the resin composition constituting the dielectric layer 3 contains at least one kind of dielectric compound and a resin component.
- the relative permittivity of the dielectric layer 3 can be adjusted according to the selection of the dielectric compound in the resin composition and its content.
- the content of the dielectric compound is preferably 10 to 300 parts by volume, and more preferably 25 to 100 parts by volume with respect to 100 parts by volume of the resin composition.
- the content of the dielectric compound is preferably 10 to 900 parts by mass, more preferably 25 to 100 parts by mass with respect to 100 parts by mass of the resin composition.
- the relative permittivity of the dielectric layer 3 tends to be sufficiently large, while when it is not more than the upper limit value, the wet coating method or There is a tendency to efficiently manufacture the dielectric layer 3 by extrusion molding.
- dielectric compounds barium titanate, titanium oxide and zinc oxide, aluminum oxide, magnesium oxide, niobium oxide, tantalum oxide, vanadium oxide, forsterite (Mg 2 SiO 4 ), barium magnesium niobate (Ba (Mg 1 / )).
- metal compounds such as 3 Nb 2/3 ) O 3
- barium neodymate titanate Ba 3 Nd 9.3 Ti 18 O 54
- gallium nitride and aluminum nitride.
- the aspect of the dielectric compound is preferably a powder (eg, nanoparticles).
- the relative permittivity of the dielectric compound is preferably higher than the relative permittivity of the resin component.
- the relative permittivity of the dielectric compound at a frequency of 3.7 GHz or 90 GHz is preferably higher than 10 and 5000 or less, more preferably 100 to 5000, and even more preferably 1000 to 5000.
- the resin component examples include acrylic resin, methacrylic resin, silicone resin, polycarbonate, epoxy resin, glyptal resin, polyvinyl chloride, polyvinylformal, phenol resin, urea resin and polychloroprene resin.
- the relative permittivity of the resin component at a frequency of 3.7 GHz or 90 GHz is preferably 2.5 to 9.5, more preferably 3.5 to 9.5, still more preferably 5.0 to 9.5. Is.
- the resin composition preferably has adhesiveness.
- the dielectric layer 3 can be efficiently attached to the surface 4F of the reflective layer 4.
- examples of such materials include silicone pressure-sensitive adhesives, acrylic pressure-sensitive adhesives and urethane pressure-sensitive adhesives. These materials may be used as the resin component, or an adhesive layer composed of these materials may be formed on at least one surface of the dielectric layer 3.
- the adhesive strength of the resin composition itself or the adhesive layer to the stainless 304 steel sheet is preferably 1.0 N / 25 mm or more, even if it is 3.0 to 10.0 N / 25 mm or 10.0 to 15.0 N / 25 mm. good.
- the complex permittivity of the dielectric layer 3 is expressed by the following equation.
- i is the imaginary unit
- ⁇ ' is the real part of the complex permittivity
- Complex permittivity ⁇ ⁇ '-i ⁇ ”
- the real part of the complex permittivity is the relative permittivity (ratio to the permittivity ⁇ 0 of vacuum).
- the relative permittivity and the dielectric loss tangent can be determined using a permittivity measuring device.
- the real part of the complex dielectric constant of the dielectric layer 3 at 3.7 GHz or 90 GHz is preferably larger than 10, more preferably 10.5 to 30, and even more preferably 12 to 20. When this value is larger than 10, it tends to be possible to achieve excellent absorption performance in a specific frequency band. On the other hand, when this value is 30 or less, the dielectric layer 3 having sufficient strength tends to be formed.
- the imaginary portion of the complex dielectric constant of the dielectric layer 3 at 3.7 GHz or 90 GHz is preferably 5 or less, more preferably 0 to 3.5, and even more preferably 0 to 3.
- the reflective layer 4 is a layer for reflecting electromagnetic waves incident from the dielectric layer 3 and reaching the dielectric layer 3.
- the thickness of the reflective layer 4 is, for example, 4 to 250 ⁇ m, and may be 4 to 12 ⁇ m or 50 to 100 ⁇ m.
- the reflective layer 4 is made of a conductive material, and it is preferable that the sheet resistance value is 100 ⁇ / ⁇ or less because electromagnetic waves can be reflected.
- a material may be an inorganic material or an organic material.
- the conductive inorganic material include zinc oxide tin (ITO), indium zinc oxide (IZO), aluminum zinc oxide (AZO), carbon nanotubes, graphene, Ag, Al, Au, Pt, Pd, Cu, Co, Cr. , In, Ag-Cu, Cu-Au and nanoparticles containing one or more selected from the group consisting of Ni nanoparticles, or nanoparticles.
- Examples of the organic material having conductivity include a polythiophene derivative, a polyacetylene derivative, a polyaniline derivative, and a polypyrrole derivative.
- a conductive inorganic material or organic material may be formed on a substrate with a thickness such that the sheet resistance is 100 ⁇ / ⁇ or less. From the viewpoints of flexibility, film forming property, stability, sheet resistance value and low cost, it is possible to use a laminated film (Al-deposited PET film) including a PET film and an aluminum layer deposited on the surface thereof as a reflective layer. preferable.
- the electromagnetic wave absorber 10 is manufactured, for example, through the following steps. First, a roll-shaped dielectric layer is produced, and then a roll-shaped laminated body including the dielectric layer is produced by a roll-to-roll method. The electromagnetic wave absorber 10 is obtained by cutting this laminated body into a predetermined size.
- the roll-shaped dielectric layer is manufactured through (A) a step of preparing the above resin composition and (B) a step of forming a dielectric layer composed of this resin composition by a roll-to-roll method.
- the thickness of the dielectric layer is sufficiently thin, so that the electromagnetic wave absorber 10 can be manufactured by the roll-to-roll method.
- the frequency band to be applied is low (for example, less than 28 GHz)
- the dielectric layer can be formed by extrusion molding. That is, the manufacturing method may be appropriately selected according to the frequency band to be applied (in other words, the thickness of the dielectric layer).
- the method for producing the dielectric layer and the laminated body is not particularly limited, and the dielectric layer and the laminated body can be produced by using conventionally known methods such as a dry laminating method and a melt-extruded laminating method.
- the dielectric layer can be produced by comma coating, die coating, extrusion film formation, or calendar film formation.
- comma coating an appropriate gap is created between the comma roll and the coating roll, the base material runs between them, a certain amount of coating liquid is applied to the film from the gap, and the film is dried to form a film. ..
- a dielectric layer having an arbitrary film thickness can be obtained by adjusting the gap.
- a dielectric layer can be produced by applying a coating liquid from a die slot to a base material conveyed on a backup roll with a gap called a coating gap and drying it.
- a dielectric layer having an arbitrary film thickness can be obtained by adjusting the supply liquid flow rate, coating gap, substrate transfer speed, and the like.
- a release-treated PET, an electromagnetic wave transmission layer, or a reflection layer can be used as before.
- the resin composition for forming the dielectric layer is supplied to a melt extruder heated to a temperature of about Tm + 100 ° C. or higher than the melting point of the resin composition to form the dielectric layer.
- the resin composition for this purpose is melted, extruded into a sheet from a die head such as a T-die, the extruded sheet is rapidly cooled and solidified by a rotating cooling drum or the like, and the dielectric layer is formed by winding. can do.
- the thickness of the dielectric layer can be controlled by the degree of opening of the "lip" that discharges the resin.
- a dielectric layer can be produced by melting a resin using a mixing roll, inserting a resin composition between two or more calendar rolls, rotating the resin, rolling, cooling, and winding the resin. The thickness of the dielectric layer can be controlled by adjusting the clearance between the calendar rolls. If the base material can be attached, it is the same as before.
- a laminated body can be produced by laminating the electromagnetic wave transmitting layer or the reflecting layer with a laminator. If the resin composition itself has no adhesiveness or the adhesive strength is small, an adhesive layer is separately prepared by using a dry laminate or the like, and the adhesive layer is applied to the resin composition itself by laminating and bonding. An adhesive layer can be imparted by laminating with an electromagnetic wave transmitting layer or a reflective layer used when the laminate is dried and made into a laminated body. Further, a laminated body can be produced by applying an adhesive to an electromagnetic wave transmitting layer or a reflective layer, drying the layer, and dry laminating the dielectric layer.
- FIG. 2 is a cross-sectional view schematically showing a reflective electromagnetic wave absorber according to the second embodiment.
- the reflective electromagnetic wave absorber 20 shown in this figure is in the form of a film or a sheet, and has a laminated structure including an electromagnetic wave transmitting layer 1, a resistance layer 5, a dielectric layer 3, and a reflecting layer 4 in this order.
- the electromagnetic wave absorber 20 has the same configuration as the electromagnetic wave absorber 10 according to the first embodiment, except that the resistance layer 5 is provided between the electromagnetic wave transmitting layer 1 and the dielectric layer 3.
- the resistance layer 5 will be described.
- the resistance layer 5 is a layer for bringing the electromagnetic wave incident from the electromagnetic wave transmitting layer 1 to the dielectric layer 3. That is, the resistance layer 5 is a layer for impedance matching according to the environment in which the electromagnetic wave absorber 20 is used and the characteristics of the electromagnetic wave transmitting layer 1. For example, when the electromagnetic wave absorber 20 is used in air (impedance: 377 ⁇ / ⁇ ), the real part (relative permittivity) of the complex dielectric constant of the dielectric layer 3 is 2.9, and the thickness is 50 ⁇ m. When the sheet resistance value of the resistance layer 5 is set in the range of 270 to 500 ⁇ / ⁇ , high reflection attenuation can be obtained.
- the resistance layer 5 is made of a conductive material.
- a material may be an inorganic material or an organic material.
- the conductive inorganic material include indium tin oxide (ITO), zinc oxide (IZO), aluminum zinc oxide (AZO), carbon nanotubes, graphene, Ag, Al, Au, Pt, Pd, Cu, and Co. , Cr, In, Ag-Cu, Cu-Au and nanoparticles containing one or more selected from the group consisting of Ni nanoparticles, or nanoparticles.
- the organic material having conductivity include a polythiophene derivative, a polyacetylene derivative, a polyaniline derivative, and a polypyrrole derivative.
- the resistance layer 5 is made of a conductive polymer containing polyethylene dioxythiophene (PEDOT) from the viewpoints of flexibility, film forming suitability of wet coating, sheet resistance stability in the atmosphere after film formation, and sheet resistance value. Is preferable.
- the resistance layer 5 may be formed of a mixture (PEDOT / PSS) of polyethylene dioxythiophene (PEDOT) and polystyrene sulfonic acid (PPS).
- the sheet resistance value of the resistance layer 5 can be appropriately set by, for example, selecting a material having conductivity and adjusting the thickness of the resistance layer 5.
- the thickness of the resistance layer 5 is preferably in the range of 0.1 to 2.0 ⁇ m, more preferably in the range of 0.1 to 0.4 ⁇ m.
- the sheet resistance value can be measured using, for example, Lorester GP MCP-T610 (trade name, manufactured by Mitsubishi Chemical Analytec Co., Ltd.).
- the relative permittivity of the dielectric layer 3 at a frequency of 3.7 GHz or 90 GHz is higher than 10.0, so that the dielectric layer 3 can be made sufficiently thin. can.
- both productivity improvement and space saving of the dielectric layer 3 can be achieved to a high level.
- a large reflection attenuation of 15 dB or more (more preferably 20 dB or more) can be achieved.
- the present invention is not limited to the above embodiments.
- the film-shaped or sheet-shaped electromagnetic wave absorbers 10 and 20 are exemplified, but the shape of the electromagnetic wave absorber is not limited to this.
- the reflective layer 4 shown in FIGS. 1 and 2 does not have to be layered.
- Resin component-Acrylic resin OC-3405 (manufactured by Saiden Chemical Co., Ltd., relative permittivity at 3.7 GHz: 4.2) -Silicone resin: MHM-SI500 (manufactured by Niei Kako Co., Ltd., relative permittivity at 3.7 GHz: 3.2) -Urethane resin: C60A10WN (manufactured by BASF Japan, Relative permittivity at 3.7 GHz: 4.5)
- Dielectric compound / barium titanate powder BT-01 (manufactured by Sakai Chemical Industry Co., Ltd.) -Titanium oxide powder: CR-60 (manufactured by Ishihara Sangyo Co., Ltd.)
- Example 1 to 3 and Comparative Examples 1 and 2 The resin compositions having the compositions shown in Table 1 were prepared respectively. The following items were evaluated for the resin compositions according to Examples and Comparative Examples.
- a dielectric layer having the thickness shown in Table 1 was formed by die coating.
- the thicknesses shown in Table 1 assume 90 GHz mobile communication. Since the thickness of the dielectric layer that can be formed by one coating is about 200 ⁇ m, only two coatings are required in Examples 1 to 3, whereas three coatings are required in Comparative Examples 1 and 2. Painting is required.
- Example 4 and comparative example 3 The resin compositions having the compositions shown in Table 2 were prepared respectively. These resin compositions were evaluated in the same manner as in Example 1 above (1) to (3) and (5). Since the urethane resin used as the resin component does not have adhesiveness, a sample in which an acrylic resin (OC-3405) to which a dielectric compound is not added is laminated on one side of a film made of a resin composition with a wire bar # 5. was prepared separately. The adhesive strength of the adhesive layer made of this acrylic resin was evaluated in the same manner as above. The evaluation of (4) was carried out as follows. (4) Evaluation of Thickness of Dielectric Layer A dielectric layer having the thickness shown in Table 2 was formed by a calendar film formation. The thickness shown in Table 2 assumes 3.7 GHz communication. The thickness of the dielectric layer that can be formed by one calendar film formation is about 800 ⁇ m.
- Example 5 and Comparative Example 4 The resin compositions having the compositions shown in Table 3 were prepared respectively. These resin compositions were evaluated in the same manner as in Example 4 above (1) to (3) and (5). The evaluation of (4) was carried out as follows. (4) Evaluation of Thickness of Dielectric Layer A dielectric layer having the thickness shown in Table 3 was formed by a calendar film formation. The thicknesses shown in Table 3 assume 28 GHz communication. However, since there is no data on the relative permittivity of the dielectric layer at 28 GHz, the thickness of the dielectric layer was set based on the relative permittivity at 3.7 GHz.
- Example 6 and Comparative Example 5 The resin compositions having the compositions shown in Table 4 were prepared respectively. These resin compositions were evaluated in the same manner as in Example 4 above (1) to (3) and (5). The evaluation of (4) was carried out as follows. (4) Evaluation of Thickness of Dielectric Layer A dielectric layer having the thickness shown in Table 4 was formed by a calendar film formation. The thicknesses shown in Table 4 assume 60 GHz communication. However, since there is no data on the relative permittivity of the dielectric layer at 60 GHz, the thickness of the dielectric layer was set based on the relative permittivity at 90 GHz.
- Example 7 and Comparative Example 6 The resin compositions having the compositions shown in Table 5 were prepared respectively. These resin compositions were evaluated in the same manner as in Example 4 above (1) to (3) and (5). The evaluation of (4) was carried out as follows. (4) Evaluation of Thickness of Dielectric Layer A dielectric layer having the thickness shown in Table 5 was formed by a calendar film formation. The thicknesses shown in Table 5 assume 350 GHz communication. However, since there is no data on the relative permittivity of the dielectric layer at 350 GHz, the thickness of the dielectric layer was set based on the relative permittivity at 90 GHz.
- Electromagnetic wave transmitting layer 3 ... Dielectric layer, 4 ... Reflecting layer, 4F ... Surface, 5 ... Resistance layer, 10, 20 ... Reflective electromagnetic wave absorber.
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Abstract
Description
d=λ/(4(εr)1/2)
式中、λは低減すべき電磁波の波長(単位:m)を示し、εrは誘電体層を構成する材料の比誘電率、dは誘電体層の厚さ(単位:m)を示す。入射する電磁波の位相と反射した電磁波の位相がπずれることで反射減衰が得られる。従来、十分な反射減衰量を達成するためには、誘電体層を厚くせざるを得なかった。このため、誘電体層の作製効率や省スペース化の点において、未だ改善の余地があった。
図1は第一実施形態に係る反射型の電磁波吸収体を模式的に示す断面図である。この図に示す電磁波吸収体10はフィルム状又はシート状であり、電磁波透過層1と誘電体層3と反射層4とをこの順序で備える積層構造を有する。なお、フィルム状の電磁波吸収体は、例えば、全体の厚さが24~250μmである。他方、シート状の電磁波吸収体は、例えば、全体の厚さが0.25~7.1mmである。
電磁波透過層1は外側から入射してきた電磁波を誘電体層3へと至らしめるための層である。すなわち、電磁波透過層1は、電磁波吸収体10が使用される環境や層構成に応じたインピーダンスマッチングをするための層であり、これにより反射減衰量が大きい電磁波吸収体10が得られる。電磁波吸収体10が空気(インピーダンス:377Ω/□)中で使用される場合、誘電体層3の比誘電率に応じて電磁波透過層1のシート抵抗を設定すればよく、例えば、3.7GHzにおける誘電体層3の比誘電率が10より大きい場合、電磁波透過層1のシート抵抗は200~800Ω/□の範囲に設定すればよく、350~400Ω/□の範囲に設定してもよい。90GHzにおける誘電体層3の比誘電率が10より大きい場合、電磁波透過層1のシート抵抗は200~800Ω/□の範囲に設定すればよく、350~400Ω/□の範囲に設定してもよい。
誘電体層3は、入射する電磁波と反射した電磁波を干渉させるための層である。誘電体層3は、以下の式で表される条件を満たすように厚さ等が設定されている。
d=λ/(4(εr)1/2)
式中、λは抑制すべき電磁波の波長(単位:m)を示し、εrは誘電体層3を構成する材料の比誘電率、dは誘電体層3の厚さ(単位:m)を示す。入射する電磁波の位相と反射した電磁波の位相がπずれることで反射減衰が得られる。
複素誘電率ε=ε’-iε”
複素誘電率の実部は比誘電率(真空の誘電率ε0に対する比)である。複素誘電率の虚部ε”の値は、誘電正接tanδ(=ε”/ε’)の値から導き出される。比誘電率及び誘電正接は誘電率測定装置を使用して求めることができる。
反射層4は誘電体層3から入射してきた電磁波を反射させ、誘電体層3へと至らしめるための層である。反射層4の厚さは、例えば、4~250μmであり、4~12μm又は50~100μmであってもよい。
電磁波吸収体10は、例えば、以下の工程を経て製造される。まず、ロール状の誘電体層を作製し、次いで、ロールtoロール方式によって誘電体層を含むロール状の積層体を作製する。この積層体を所定のサイズに切断することで電磁波吸収体10が得られる。ロール状の誘電体層は、(A)上記樹脂組成物を調製する工程と、(B)この樹脂組成物からなる誘電体層をロールtoロール方式によって形成する工程とを経て製造される。適用対象の周波数帯が高い場合(例えば、60GHz以上)、誘電体層の厚さが十分に薄いため、ロールtoロール方式によって電磁波吸収体10を製造できる。これに対し、適用対象の周波数帯が低い場合(例えば、28GHz未満)、誘電体層を厚く形成する必要があるため、ロールtoロール方式での製造が困難となる傾向にある。この場合、例えば、押出し成形によって誘電体層を形成することができる。つまり、適用対象の周波数帯(換言すれば、誘電体層の厚さ)に応じて作製方法を適宜選択すればよい。
図2は第二実施形態に係る反射型の電磁波吸収体を模式的に示す断面図である。この図に示す反射型の電磁波吸収体20はフィルム状又はシート状であり、電磁波透過層1と抵抗層5と誘電体層3と反射層4とをこの順序で備える積層構造を有する。電磁波吸収体20は、電磁波透過層1と誘電体層3との間に、抵抗層5を備えることの他は、第一実施形態に係る電磁波吸収体10と同様の構成である。以下、抵抗層5について説明する。
抵抗層5は電磁波透過層1から入射してきた電磁波を誘電体層3へと至らしめるための層である。すなわち、抵抗層5は、電磁波吸収体20が使用される環境や、電磁波透過層1の特性に応じてインピーダンスマッチングをするための層である。例えば、電磁波吸収体20が空気(インピーダンス:377Ω/□)中で使用され、且つ誘電体層3の複素誘電率の実部(比誘電率)が2.9であり、厚さが50μmの場合、抵抗層5のシート抵抗値を270~500Ω/□の範囲に設定すると高い反射減衰を得ることができる。
(1)樹脂成分
・アクリル樹脂:OC-3405(サイデン化学社製、3.7GHzにおける比誘電率:4.2)
・シリコーン樹脂:MHM-SI500(日榮加工社製、3.7GHzにおける比誘電率:3.2)
・ウレタン樹脂:C60A10WN(BASFジャパン社製、3.7GHzにおける比誘電率:4.5)
(2)誘電性化合物
・チタン酸バリウム粉末:BT-01(堺化学工業社製)
・酸化チタン粉末:CR-60(石原産業社製)
表1に示す組成の樹脂組成物をそれぞれ調製した。実施例及び比較例に係る樹脂組成物について、以下の項目について評価を行った。
JIS C2138:2007に記載の方法に準拠し、空洞共振器法誘電率測定装置を用いて、周波数1MHzから1GHzの範囲で樹脂組成物の比誘電率を温度25℃、相対湿度50%の条件下で測定した。各水準にて5つの試料を準備し、測定を5回行った。周波数1MHz、500MHz及び1GHzの3つの比誘電率の測定値を片対数グラフにプロットして近似直線を引いた。なお、周波数を横軸(ログスケール)とし、比誘電率の値を縦軸をとした。この近似直線から3.7GHz及び90GHzにおける比誘電率を算出した。5回の測定から算出された比誘電率の値を表1に記載した。
JIS Z0237:2009に記載の方法に準拠し、樹脂組成物の粘着力を評価した。実施例及び比較例に係る樹脂組成物を厚さ0.2mmのフィルムに加工した後、これを切断して幅25mmの試料を得た。他方、一方の面が鏡面仕上げされたステンレス304鋼板を準備した。この面上に試料を配置した後、2kgのローラーを2往復させて圧着した。30分静置させた後、引張試験機を用いて試料をステンレス304鋼板に対して180°の角度で剥離して剥離強度を測定した。剥離速度は300mm/分とした。結果を表1に示した。
アクリル樹脂(OC-3405)は粘着性を有するものの、表1の実施例2,3の結果に示されたとおり、誘電性化合物の体積分率増加に伴って樹脂組成物の粘着力が低くなった。そのため、実施例2,3に係る樹脂組成物で作製したフィルムの片面に誘電性化合物未添加のアクリル樹脂(OC-3405)をワイヤーバー#5にて積層した試料を別途作製した。このアクリル樹脂からなる粘着層の粘着力を上記と同様にして評価した。結果を表1に示した。
表1に示す厚さの誘電体層をダイ塗工によって形成した。表1に示す厚さは、90GHz移動通信を想定したものである。なお、1回の塗工で形成可能な誘電体層の厚さは200μm程度であるため、実施例1~3では2回の塗工で済むのに対し、比較例1,2では3回の塗工が必要である。
最大巻径700mmの装置にて、巻径内径3インチ、肉厚4mm(外径84.2mm)のコアに巻取を行うことを想定した場合の巻メートル数を表1に示す。実施例1~3では一つのロールに1450mを超える誘電体を巻くことができるのに対し、比較例1,2では一つのロールに1000m以下の誘電体を巻けるにとどまる。
表2に示す組成の樹脂組成物をそれぞれ調製した。これらの樹脂組成物について、実施例1と同様にして上記(1)~(3)及び(5)の評価を行った。なお、樹脂成分として使用したウレタン樹脂は粘着性を有しないため、樹脂組成物で作製したフィルムの片面に誘電性化合物未添加のアクリル樹脂(OC-3405)をワイヤーバー#5にて積層した試料を別途作製した。このアクリル樹脂からなる粘着層の粘着力を上記と同様にして評価した。また、(4)の評価は以下のとおり実施した。
(4)誘電体層の厚さについての評価
表2に示す厚さの誘電体層をカレンダー製膜によって形成した。表2に示す厚さは、3.7GHz通信を想定したものである。なお、1回のカレンダー製膜で形成可能な誘電体層の厚さは800μm程度である。
表3に示す組成の樹脂組成物をそれぞれ調製した。これらの樹脂組成物について、実施例4と同様にして上記(1)~(3)及び(5)の評価を行った。(4)の評価は以下のとおり実施した。
(4)誘電体層の厚さについての評価
表3に示す厚さの誘電体層をカレンダー製膜によって形成した。表3に示す厚さは、28GHz通信を想定したものである。ただし、28GHzにおける誘電体層の比誘電率のデータがないため、3.7GHzにおける比誘電率をもとに誘電体層の厚さを設定した。
表4に示す組成の樹脂組成物をそれぞれ調製した。これらの樹脂組成物について、実施例4と同様にして上記(1)~(3)及び(5)の評価を行った。(4)の評価は以下のとおり実施した。
(4)誘電体層の厚さについての評価
表4に示す厚さの誘電体層をカレンダー製膜によって形成した。表4に示す厚さは、60GHz通信を想定したものである。ただし、60GHzにおける誘電体層の比誘電率のデータがないため、90GHzにおける比誘電率をもとに誘電体層の厚さを設定した。
表5に示す組成の樹脂組成物をそれぞれ調製した。これらの樹脂組成物について、実施例4と同様にして上記(1)~(3)及び(5)の評価を行った。(4)の評価は以下のとおり実施した。
(4)誘電体層の厚さについての評価
表5に示す厚さの誘電体層をカレンダー製膜によって形成した。表5に示す厚さは、350GHz通信を想定したものである。ただし、350GHzにおける誘電体層の比誘電率のデータがないため、90GHzでの比誘電率をもとに誘電体層の厚さを設定した。
Claims (12)
- 反射型の電磁波吸収体が備える誘電体層の製造方法であって、
少なくとも一種の誘電性化合物と、樹脂成分とを含有し、周波数3.7GHzにおける比誘電率が10.0よりも高い樹脂組成物を調製する工程と、
前記樹脂組成物からなる厚さ20~7000μmの誘電体層を形成する工程と、
を含む、誘電体層の製造方法。 - 反射型の電磁波吸収体が備える誘電体層の製造方法であって、
少なくとも一種の誘電性化合物と、樹脂成分とを含有し、周波数90GHzにおける比誘電率が10.0よりも高い樹脂組成物を調製する工程と、
前記樹脂組成物からなる厚さ20~7000μmの誘電体層を形成する工程と、
を含む、誘電体層の製造方法。 - 反射型の電磁波吸収体が備える誘電体層の形成に用いられる樹脂組成物であって、
少なくとも一種の誘電性化合物と、
樹脂成分と、
を含有し、
周波数3.7GHzにおける比誘電率が10.0よりも高い、樹脂組成物。 - 反射型の電磁波吸収体が備える誘電体層の形成に用いられる樹脂組成物であって、
少なくとも一種の誘電性化合物と、
樹脂成分と、
を含有し、
周波数90GHzにおける比誘電率が10.0よりも高い、樹脂組成物。 - 前記誘電性化合物の比誘電率が前記樹脂成分の比誘電率よりも高い、請求項3又は4に記載の樹脂組成物。
- 粘着性を有する、請求項3~5のいずれか一項に記載の樹脂組成物。
- ステンレス304鋼板に対する粘着力が1.0N/25mm以上である、請求項6に記載の樹脂組成物。
- 前記誘電性化合物が金属化合物である、請求項3~7のいずれか一項に記載の樹脂組成物。
- 前記金属化合物が酸化チタン及びチタン酸バリウムの少なくとも一方である、請求項8に記載の樹脂組成物。
- 前記樹脂成分の周波数3.7GHzにおける比誘電率が2.5~9.5である、請求項3~9のいずれか一項に記載の樹脂組成物。
- 前記樹脂成分の周波数90GHzにおける比誘電率が2.5~9.5である、請求項3~9のいずれか一項に記載の樹脂組成物。
- 請求項3~11のいずれか一項に記載の樹脂組成物からなる誘電体層と、
前記誘電体層の少なくとも一方の面上に設けられた粘着層と、
を備える、積層体。
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