WO2020196368A1 - λ/4 RADIOWAVE ABSORBER - Google Patents

λ/4 RADIOWAVE ABSORBER Download PDF

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Publication number
WO2020196368A1
WO2020196368A1 PCT/JP2020/012618 JP2020012618W WO2020196368A1 WO 2020196368 A1 WO2020196368 A1 WO 2020196368A1 JP 2020012618 W JP2020012618 W JP 2020012618W WO 2020196368 A1 WO2020196368 A1 WO 2020196368A1
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Prior art keywords
radio wave
weight
layer
wave absorber
resistance
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PCT/JP2020/012618
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French (fr)
Japanese (ja)
Inventor
哲郎 澤田石
幸子 中尾
勝紀 武藤
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積水化学工業株式会社
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Priority to JP2021509367A priority Critical patent/JPWO2020196368A1/ja
Publication of WO2020196368A1 publication Critical patent/WO2020196368A1/en

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    • 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
    • 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

Definitions

  • the present invention relates to a ⁇ / 4 type radio wave absorber and the like.
  • Patent Document 1 discloses an electromagnetic wave absorber having a bandwidth of 2 GHz or more in a frequency band having an electromagnetic wave absorption amount of 20 dB or more in a frequency band of 60 to 90 GHz.
  • radio absorbers that absorb high frequency radio waves in a wide frequency range.
  • these radio wave absorbers are used as parts for devices mounted on automobiles and the like, they need to have thermal and cooling durability that can cope with drastic changes in temperature. I paid attention to it.
  • an object of the present invention is to provide a ⁇ / 4 type radio wave absorber that can exhibit a certain level of radio wave absorption from a low temperature to a high temperature (particularly, a high temperature of 100 ° C. or higher).
  • the present inventor considers a ⁇ / 4 type radio wave absorber having a minimum value of radio wave absorption at 79 GHz at 60 to 130 ° C. of 10 dB or more. I found that I could solve the problem. The present inventor has completed the present invention as a result of further research based on this finding.
  • the present invention includes the following aspects.
  • Item 1 A ⁇ / 4 type radio wave absorber in which the minimum value of the radio wave absorption amount at 79 GHz at 60 to 130 ° C. is 10 dB or more.
  • Item 2 The ⁇ / 4 type radio wave absorber according to Item 1, which includes a dielectric layer and has a glass transition temperature Tg of the dielectric layer of ⁇ 10 ° C. or higher.
  • Item 3 The ⁇ / 4 type radio wave absorber according to Item 1 or 2, which includes a dielectric layer and has a relative permittivity of 1 to 5 of the dielectric layer.
  • Item 4. The ⁇ / 4 type radio wave absorber according to any one of Items 1 to 3, which includes a support and has a glass transition temperature Tg of the support of 40 ° C. or higher.
  • Item 5 The ⁇ / 4 type radio wave absorber according to Item 4, wherein the absolute value of the heat shrinkage rate is 0.5% or less in both the MD direction and the TD direction after heating the support at 150 ° C. for 60 minutes.
  • Item 6 The ⁇ / 4 type radio wave absorber according to any one of Items 1 to 5, which includes a support and has a relative permittivity of 1 to 5 of the support.
  • Item 7 A millimeter-wave radar including the ⁇ / 4 type radio wave absorber according to any one of Items 1 to 6.
  • the minimum value of the radio wave absorption at 79 GHz at 60 to 130 ° C. is 10 dB or more.
  • a ⁇ / 4 type radio wave absorber that can exhibit a certain level of radio wave absorption or higher from a low temperature to a high temperature (particularly, a high temperature of 100 ° C. or higher).
  • the upper figure is a schematic cross-sectional view showing an example of a member for a radio wave absorber of the present invention.
  • the lower part is a schematic cross-sectional view showing an example of an adherend that can function as a reflective layer and is arranged so that the members are in contact with each other.
  • a ⁇ / 4 type radio wave absorber having a minimum value of radio wave absorption at 79 GHz at 60 to 130 ° C. of 10 dB or more (in the present specification, " ⁇ / 4 type of the present invention”.
  • radio wave absorber Sometimes referred to as "radio wave absorber”). This will be described below.
  • the ⁇ / 4 type radio wave absorber of the present invention has a characteristic that the minimum value of the radio wave absorption amount at 79 GHz at 60 to 130 ° C. is 10 dB or more (also referred to as “characteristic of the present invention” in the present specification. There is.) By having this characteristic, it is possible to exhibit a certain level of radio wave absorption not only in a high temperature range (particularly, a high temperature of 100 ° C. or higher) but also in a wide temperature range from low temperature to high temperature.
  • the minimum value of the radio wave absorption amount is preferably 10 dB or more, more preferably 15 dB or more.
  • the upper limit of the radio wave absorption amount is not particularly limited, and is not particularly limited, for example, 40 dB, 30 dB, and 25 dB.
  • the characteristics of the present invention can be measured as follows.
  • Network analyzer MS4647B manufactured by Anritsu
  • free space material measurement device BD1-26 A radio wave absorption measuring device is configured using A (manufactured by Keycom).
  • the radio wave absorption amount of the obtained ⁇ / 4 type radio wave electromagnetic wave absorber at 79 GHz can be measured based on JIS R1679.
  • the ⁇ / 4 type radio wave absorber is set so that the radio wave incident direction is vertical incident.
  • the temperature of the radio wave absorber is adjusted by heating with a polyimide heater or the like from the surface opposite to the surface on which the radio wave is incident.
  • the temperature of the radio wave absorber can be measured using an infrared radiation thermometer (AD-5613A (manufactured by A & D Co., Ltd.) or an equivalent product thereof).
  • the configuration of the ⁇ / 4 type radio wave absorber of the present invention is not particularly limited as long as it has the above-mentioned characteristics of the present invention, and for example, a known configuration of the radio wave absorber can be adopted.
  • the ⁇ / 4 type radio wave absorber of the present invention has a configuration having a resistance film, a dielectric layer, and a reflection layer.
  • the ⁇ / 4 type radio wave absorber of the present invention includes a support, a resistance film, a dielectric layer, and a reflection layer.
  • the ⁇ / 4 type radio wave absorber of the present invention has a resistance film
  • the resistance film can be protected and the durability as a radio wave absorber can be enhanced.
  • the support is not particularly limited as long as it is in the form of a sheet.
  • the support is not particularly limited, and examples thereof include a resin base material.
  • the resin base material is a base material containing resin as a material, and is not particularly limited as long as it is in the form of a sheet.
  • the resin base material may contain components other than the resin as long as the effects of the present invention are not significantly impaired.
  • titanium oxide or the like may be contained from the viewpoint of adjusting the relative permittivity or the like.
  • the total amount of the resin in the resin base material is, for example, 80% by mass or more, preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably 99% by mass or more, and usually less than 100% by mass.
  • the resin is not particularly limited, and is, for example, a polyester resin such as polyethylene terephthalate (PET), polyethylene naphthalate, or modified polyester, a polyolefin such as a polyethylene (PE) resin, a polypropylene (PP) resin, a polystyrene resin, or a cyclic olefin resin.
  • vinyl-based resins such as polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, polyvinyl acetal resin such as polyvinyl butyral (PVB), polyether ether ketone (PEEK) resin, polysalphon (PSF) resin, polyether salphon
  • PVB polyvinyl butyral
  • PEEK polyether ether ketone
  • PSF polysalphon
  • PES polycarbonate
  • PC polyamide resin
  • polyimide resin polyimide resin
  • acrylic resin acrylic resin
  • TAC triacetyl cellulose
  • polyester-based resins are preferable, and polyethylene terephthalate is more preferable, from the viewpoints of productivity and strength, the characteristics of the present invention, and the like.
  • the relative permittivity of the support is not particularly limited.
  • the relative permittivity of the support is, for example, 1 to 20, preferably 1 to 15, and more preferably 1 to 10. Above all, the relative permittivity of the support is particularly preferably 1 to 5 from the viewpoint that the temperature change of the permittivity can be suppressed to a lower level.
  • the specific dielectric constant of the support can be measured in the same manner as the specific dielectric constant of the dielectric layer described later.
  • the glass transition temperature Tg of the support is not particularly limited as long as it can satisfy the characteristics of the present invention.
  • the glass transition temperature Tg of the support is preferably 20 ° C. or higher, more preferably 30 ° C. or higher, still more preferably 40 ° C. or higher, still more preferably 50 ° C. or higher, and particularly preferably 60 ° C. or higher. ° C. or higher, particularly preferably 70 ° C. or higher.
  • the upper limit of the temperature is not particularly limited, and is, for example, 250 ° C, 200 ° C, and 150 ° C.
  • the heat shrinkage rate of the support is not particularly limited as long as it can satisfy the characteristics of the present invention.
  • the absolute value of the heat shrinkage of the support is preferably 0.5% or less, more preferably 0.4% or less, still more preferably 0.3% or less from the viewpoint of the characteristics of the present invention in both the MD direction and the TD direction. Is.
  • the lower limit of the shrinkage rate is not particularly limited, and is, for example, 0%, 0.01%, and 0.1%.
  • the heat shrinkage of the support can be measured based on JISZ1715: 2009. Specifically, after cutting the support into 20 mm ⁇ 150 mm in the MD direction and the TD direction, respectively, a marked line at intervals of 50 mm is attached to the central portion in the length direction of the test piece.
  • the heat shrinkage rate in the MD direction and the TD direction can be obtained from the following formula by measuring the distance between the marked lines after heating at 150 ° C. for 60 minutes and leaving the mixture at room temperature for 30 minutes (JISZ1715: 2009).
  • the heat shrinkage rate is a negative value, it means that the material has expanded after heating.
  • S (L1-L2) x 100 / L1
  • S the heating shrinkage rate (%)
  • L1 the distance between the marked lines before heating
  • L2 the distance between the marked lines after heating.
  • the method for adjusting the heat shrinkage rate is not particularly limited, and for example, a method using a resin sheet satisfying the heat shrinkage rate as a support, a method of performing a stretching treatment, a heat annealing treatment, a prior heat shrinkage treatment, or the like on the support. It can be adjusted by such means.
  • the thickness of the support is not particularly limited.
  • the thickness of the support is, for example, 5 ⁇ m or more and 500 ⁇ m or less, preferably 10 ⁇ m or more and 300 ⁇ m or less, and more preferably 20 ⁇ m or more and 300 ⁇ m or less.
  • the thickness of the support is preferably 30 ⁇ m or more and 250 ⁇ m or less, and more preferably 40 ⁇ m or more and 200 ⁇ m or less.
  • the layer structure of the support is not particularly limited.
  • the support may be composed of one type of support alone, or may be a combination of two or more types of supports.
  • the resistance film is not particularly limited as long as it includes a layer that can function as a resistance layer in the radio wave absorber.
  • the resistance value of the resistance film is not particularly limited.
  • the resistance value of the resistance film is, for example, 200 to 600 ⁇ / ⁇ . Within this range, it is more preferably 220 to 550 ⁇ / ⁇ , and even more preferably 250 to 500 ⁇ / ⁇ .
  • the resistance value of the resistance film can be measured by the 4-terminal method using a surface resistance meter (manufactured by MITSUBISHI CHEMICALANALYTECH, trade name "Loresta-EP”).
  • a surface resistance meter manufactured by MITSUBISHI CHEMICALANALYTECH, trade name "Loresta-EP”
  • a non-contact resistance meter product name "EC-80P, manufactured by Napson, or an equivalent product
  • the thickness of the resistance film is not particularly limited.
  • the thickness of the resistance film is, for example, 1 nm or more and 200 nm or less, preferably 2 nm or more and 100 nm or less, and more preferably 2 nm or more and 50 nm or less.
  • the layer structure of the resistance film is not particularly limited.
  • the resistance film may be composed of a single layer of one type, or may be a combination of a plurality of layers of two or more types.
  • ITO-containing resistance layer for example, indium tin oxide (hereinafter referred to as "ITO") is used. Among them, SnO 2 of 1 to 40% by weight, more preferably 2 to 35, because the amorphous structure is extremely stable and the fluctuation of the sheet resistance of the resistance layer can be suppressed even in a high temperature and high humidity environment. Those containing ITO containing% by weight SnO 2 are preferably used.
  • the content of ITO in the resistance layer is, for example, 50% by mass or more, preferably 70% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and usually less than 100% by mass.
  • Molybdenum-containing resistance layer As the resistance layer, a resistance layer containing molybdenum is preferably used from the viewpoint of durability and easy adjustment of sheet resistance.
  • the lower limit of the molybdenum content is not particularly limited, but from the viewpoint of further enhancing durability, 5% by weight is preferable, 7% by weight is more preferable, 9% by weight is further preferable, 11% by weight is further preferable, and 13% by weight is used. % Is particularly preferred, 15% by weight is very preferred, and 16% by weight is most preferred.
  • the upper limit of the molybdenum content is preferably 70% by weight, more preferably 30% by weight, further preferably 25% by weight, still more preferably 20% by weight, from the viewpoint of facilitating adjustment of the surface resistance value. ..
  • the resistance layer contains molybdenum
  • nickel and chromium in addition to molybdenum in the resistance layer, a more durable radio wave absorber can be obtained.
  • alloys containing nickel, chromium and molybdenum include Hasteroy B-2, B-3, C-4, C-2000, C-22, C-276, G-30, N, W and X. Various grades can be mentioned.
  • the resistance layer contains molybdenum, nickel and chromium
  • the molybdenum content is 5% by weight or more
  • the nickel content is 40% by weight or more
  • the chromium content is 1% by weight or more.
  • the molybdenum, nickel and chromium contents are more preferably 7% by weight or more, nickel content of 45% by weight or more, and chromium content of 3% by weight or more.
  • the molybdenum, nickel and chromium contents are more preferably 9% by weight or more, the nickel content is 47% by weight or more, and the chromium content is 5% by weight or more.
  • the molybdenum, nickel and chromium contents are more preferably 11% by weight or more, the nickel content is 50% by weight or more, and the chromium content is 10% by weight or more.
  • the contents of molybdenum, nickel and chromium it is particularly preferable that the molybdenum content is 13% by weight or more, the nickel content is 53% by weight or more, and the chromium content is 12% by weight or more.
  • the molybdenum content is 15% by weight or more, the nickel content is 55% by weight or more, and the chromium content is 15% by weight or more.
  • the molybdenum, nickel and chromium contents are most preferably 16% by weight or more, nickel content is 57% by weight or more, and chromium content is 16% by weight or more.
  • the nickel content is preferably 80% by weight or less, more preferably 70% by weight or less, and further preferably 65% by weight or less.
  • the upper limit of the chromium content is preferably 50% by weight or less, more preferably 40% by weight or less, and further preferably 35% by weight or less.
  • the resistance layer may contain a metal other than molybdenum, nickel and chromium.
  • metals include iron, cobalt, tungsten, manganese, titanium and the like.
  • the upper limit of the total content of metals other than molybdenum, nickel and chromium is preferably 45% by weight, more preferably 40, from the viewpoint of durability of the resistance layer. It is by weight%, more preferably 35% by weight, even more preferably 30% by weight, particularly preferably 25% by weight, and very preferably 23% by weight.
  • the lower limit of the total content of the metals other than molybdenum, nickel and chromium is, for example, 1% by weight or more.
  • the preferable upper limit of the content is 25% by weight, the more preferable upper limit is 20% by weight, the further preferable upper limit is 15% by weight, and the preferable lower limit is 15% by weight from the viewpoint of the durability of the resistance layer. It is 1% by weight.
  • the preferable upper limit of the content is 5% by weight, the more preferable upper limit is 4% by weight, and the further preferable upper limit is independently from the viewpoint of the durability of the resistance layer. It is 3% by weight, and the preferable lower limit is 0.1% by weight.
  • the preferable upper limit of the content is 8% by weight, the more preferable upper limit is 6% by weight, the further preferable upper limit is 4% by weight, and the preferable lower limit is 4% by weight from the viewpoint of the durability of the resistance layer. It is 1% by weight.
  • the resistance layer may contain silicon and / or carbon.
  • the content of silicon and / or carbon is preferably 1% by weight or less, and more preferably 0.5% by weight or less, respectively. ..
  • the content of the silicon and / or carbon is preferably 0.01% by weight or more.
  • the resistance value of the resistance layer is not particularly limited.
  • the resistance value of the resistance layer is, for example, 200 to 600 ⁇ / ⁇ . Within this range, it is more preferably 220 to 550 ⁇ / ⁇ , and even more preferably 250 to 500 ⁇ / ⁇ .
  • the thickness of the resistance layer is not particularly limited.
  • the thickness of the resistance layer is, for example, 1 nm or more and 200 nm or less, preferably 2 nm or more and 100 nm or less, and more preferably 2 nm or more and 50 nm or less.
  • the layer structure of the resistance layer is not particularly limited.
  • the resistance layer may be composed of one type of resistance layer alone, or may be a combination of two or more types of resistance layers.
  • the resistance film preferably contains a barrier layer.
  • the barrier layer is placed on at least one surface of the resistance layer. The barrier layer will be described in detail below.
  • the barrier layer is not particularly limited as long as it is a layer that can protect the resistance layer and suppress its deterioration.
  • the material of the barrier layer include metal compounds, metalloid compounds, preferably metal or metalloid oxides, nitrides, nitride oxides and the like.
  • the barrier layer may contain components other than the above materials as long as the effects of the present invention are not significantly impaired.
  • the amount of the material in the barrier layer is, for example, 80% by mass or more, preferably 90% by mass or more, more preferably 95% by mass or more, further preferably 99% by mass or more, and usually less than 100% by mass. ..
  • Examples of the metal element contained in the barrier layer include titanium, aluminum, niobium, cobalt, nickel and the like.
  • Examples of the metalloid element contained in the barrier layer include silicon, germanium, antimony, bismuth and the like.
  • MO X is a number satisfying the formula: n / 100 ⁇ X ⁇ n / 2 (n is a valence of a metal or a semi-metal), and M is a metal element or It is a semi-metallic element. ] Examples thereof include compounds represented by.
  • nitride for example, MN y [in the formula, Y is a number satisfying the formula: n / 100 ⁇ Y ⁇ n / 3 (n is a valence of a metal or a semi-metal), and M is a metal element or It is a semi-metallic element. ], Examples thereof include compounds represented by.
  • nitride oxide examples include MO X N y [in the formula, X and Y are n / 100 ⁇ X, n / 100 ⁇ Y, and X + Y ⁇ n / 2 (n is a valence of a metal or a metalloid). ), And M is a metal element or a metalloid element. ], Examples thereof include compounds represented by.
  • the oxidation number X of the oxide or oxynitride for example MO a cross-section of the layer containing the x or MO x N y, FE-TEM -EDX (e.g., manufactured by JEOL Ltd. "JEM-ARM200F") Elemental analysis Then, the valence of the oxygen atom can be calculated by calculating X from the elemental ratio of M and O per area of the cross section of the layer containing MO x or MO x N y .
  • the cross section of the layer containing MN y or MO x N y is elementalized by FE-TEM-EDX (for example, "JEM-ARM200F” manufactured by JEOL Ltd.).
  • the valence of nitrogen atoms can be calculated by analyzing and calculating Y from the elemental ratio of M and N per area of the cross section of the layer containing MN y or MO x N y .
  • the material of the barrier layer include SiO 2 , SiO x , Al 2 O 3 , MgAl 2 O 4 , CuO, CuN, TiO 2 , TiN, AZO (aluminum-doped zinc oxide) and the like.
  • the thickness of the barrier layer is not particularly limited.
  • the thickness of the barrier layer is, for example, 1 nm or more and 200 nm or less, preferably 1 nm or more and 100 nm or less, and more preferably 1 nm or more and 20 nm or less.
  • the layer structure of the barrier layer is not particularly limited.
  • the barrier layer may be composed of one type of barrier layer alone, or may be a combination of two or more types of barrier layers.
  • the dielectric layer is not particularly limited as long as it can function as a dielectric for a target wavelength in the radio wave absorber.
  • the dielectric layer is not particularly limited, and examples thereof include a resin sheet and an adhesive.
  • the resin sheet is not particularly limited as long as it is in the form of a sheet containing resin as a material.
  • the resin sheet may contain components other than the resin as long as the effects of the present invention are not significantly impaired.
  • the total amount of the resin in the resin sheet is, for example, 50% by mass or more, preferably 70% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and usually less than 100% by mass. is there.
  • the resin is not particularly limited, for example, ethylene vinyl acetate copolymer (EVA), vinyl chloride, urethane, acrylic, acrylic urethane, polyolefin, polyethylene, polypropylene, silicone, polyethylene terephthalate, polyester, polystyrene, polyimide, polycarbonate, polyamide. , Polysulfone, polyether sulfone, epoxy and other synthetic resins, polyisoprene rubber, polystyrene / butadiene rubber, polybutadiene rubber, chloroprene rubber, acrylonitrile / butadiene rubber, butyl rubber, acrylic rubber, ethylene / propylene rubber and silicone rubber. It is preferable to use a rubber material as a resin component. These can be used alone or in combination of two or more.
  • EVA ethylene vinyl acetate copolymer
  • vinyl chloride urethane
  • acrylic acrylic urethane
  • polyolefin polyethylene
  • polypropylene silicone
  • the dielectric layer may be a foam or an adhesive.
  • the adhesive is not particularly limited, and for example, acrylic adhesive, urethane adhesive, polyolefin adhesive, polyester adhesive, vinyl alkyl ether adhesive, polyamide adhesive, rubber adhesive, silicone adhesive. Examples include adhesives and fluorine-based adhesives. Among these, an acrylic adhesive is preferable from the viewpoint of high weather resistance.
  • the dielectric layer may have adhesiveness. Therefore, when a dielectric having no adhesiveness is laminated on another layer by the pressure-sensitive adhesive layer, the combination of the dielectric and the pressure-sensitive adhesive layer becomes a "dielectric layer".
  • the dielectric layer preferably includes an adhesive layer from the viewpoint of easy stacking with the adjacent layer.
  • the relative permittivity of the dielectric layer is not particularly limited as long as it can satisfy the characteristics of the present invention.
  • the relative permittivity of the dielectric layer is, for example, 1 to 20, preferably 1 to 15, and more preferably 1 to 10.
  • the relative permittivity of the dielectric layer is particularly preferably 1 to 5 from the viewpoint that the temperature change of the dielectric constant can be suppressed to a lower level.
  • the relative permittivity of the dielectric layer can be measured at 1 MHz with a dielectric constant measuring device (Precision LCR meter E4980AL) manufactured by Keysight and a measuring electrode (DPT-2141-01) manufactured by Keycom.
  • a dielectric constant measuring device Precision LCR meter E4980AL
  • DPT-2141-01 measuring electrode
  • the glass transition temperature Tg of the dielectric layer is not particularly limited as long as it can satisfy the characteristics of the present invention. From the viewpoint of the characteristics of the present invention, the glass transition temperature Tg of the dielectric layer is preferably ⁇ 10 ° C. or higher, more preferably ⁇ 8 ° C. or higher, still more preferably ⁇ 6 ° C. or higher.
  • the upper limit of the temperature is not particularly limited, and is, for example, 150 ° C. and 200 ° C.
  • the glass transition temperature Tg of the dielectric layer is measured using a dynamic viscoelasticity measuring device (ARES-G2 (manufactured by TA Instruments) or its equivalent) at a frequency of 10 Hz and a temperature range of -100 ° C to 250 ° C. It can be measured by calculating the glass transition temperature Tg.
  • ADS-G2 dynamic viscoelasticity measuring device
  • the thickness of the dielectric layer is not particularly limited as long as it can satisfy the characteristics of the present invention.
  • the thickness of the dielectric layer is, for example, 100 to 1000 ⁇ m. From the viewpoint of the characteristics of the present invention, the thickness is preferably 150 to 900 ⁇ m, more preferably 200 to 800 ⁇ m.
  • the thickness of the dielectric layer can be measured by Nikon DIGIMICRO STANDMS-11C + Nikon DIGIMICRO MFC-101.
  • the layer structure of the dielectric layer is not particularly limited.
  • the dielectric layer may be composed of one kind of single dielectric layer, or may be a combination of two or more kinds of dielectric layers.
  • a three-layered dielectric layer composed of a non-adhesive dielectric and adhesive layers arranged on both sides thereof, a one-layered dielectric layer composed of an adhesive dielectric, and the like can be mentioned.
  • the reflective layer is not particularly limited as long as it can function as a radio wave reflecting layer in the radio wave absorber.
  • the reflective layer is not particularly limited, and examples thereof include a metal film.
  • the metal film is not particularly limited as long as it is a layer containing metal as a material.
  • the metal film may contain a component other than the metal as long as the effect of the present invention is not significantly impaired.
  • the total amount of the metal in the metal film is, for example, 30% by mass or more, preferably 50% by mass or more, more preferably 75% by mass or more, still more preferably 80% by mass or more, still more preferably 90% by mass or more. , Particularly preferably 95% by mass or more, very preferably 99% by mass or more, and usually less than 100% by mass.
  • the metal is not particularly limited, and examples thereof include aluminum, copper, iron, silver, gold, chromium, nickel, molybdenum, gallium, zinc, tin, niobium, and indium. Further, a metal compound such as ITO can also be used as a material for the metal film. These may be one kind alone or a combination of two or more kinds.
  • the thickness of the reflective layer is not particularly limited.
  • the thickness of the reflective layer is, for example, 1 ⁇ m or more and 500 ⁇ m or less, preferably 2 ⁇ m or more and 200 ⁇ m or less, and more preferably 5 ⁇ m or more and 100 ⁇ m or less.
  • the layer structure of the reflective layer is not particularly limited.
  • the reflective layer may be composed of one type of single reflective layer, or may be a combination of a plurality of two or more types of reflective layers.
  • the ⁇ / 4 type radio wave absorber of the present invention has a resistance film, a dielectric layer, and a reflective layer
  • the layers are arranged in the order in which the radio wave absorption performance can be exhibited.
  • the resistance film, the dielectric layer, and the reflective layer are arranged in this order.
  • the ⁇ / 4 type radio wave absorber of the present invention has a support
  • the support, the resistance film, the dielectric layer, and the reflective layer are arranged in this order as an example.
  • the ⁇ / 4 type radio wave absorber of the present invention may include other layers in addition to the support, the resistance film, the dielectric layer, and the reflective layer.
  • the other layer may be placed on the surface of either the support, the resistor film, the dielectric layer, and the reflective layer, respectively.
  • the ⁇ / 4 type radio absorber of the present invention can be obtained according to or according to various methods, for example, a known manufacturing method, depending on its configuration. For example, it can be obtained by a method including a step of sequentially laminating a resistance film, a dielectric layer, and a reflective layer on a support.
  • the stacking method is not particularly limited.
  • the resistance film can be formed by, for example, a sputtering method, a vacuum vapor deposition method, an ion plating method, a chemical vapor deposition method, a pulse laser deposition method, or the like.
  • the sputtering method is preferable from the viewpoint of film thickness controllability.
  • the sputtering method is not particularly limited, and examples thereof include DC magnetron sputtering, high frequency magnetron sputtering, and ion beam sputtering.
  • the sputtering apparatus may be a batch system or a roll-to-roll system.
  • the dielectric layer and the reflective layer can be laminated by utilizing, for example, the adhesiveness of the dielectric layer.
  • ⁇ / 4 type radio wave absorber member there is a radio wave at 79 GHz at 60 to 130 ° C. when a reflective layer made of copper having a thickness of 30 ⁇ m including a resistance film and a dielectric layer is laminated on the other surface of the dielectric layer.
  • the present invention relates to a ⁇ / 4 type radio wave absorber member having a minimum absorption amount of 10 dB or more.
  • a reflective layer made of copper having a thickness of 30 ⁇ m a copper plate or copper foil tape having a surface roughness (Ra) of 0.3 nm on the surface in contact with the dielectric layer is used.
  • the ⁇ / 4 type radio wave absorber member is a member for forming a ⁇ / 4 type radio wave absorber by arranging it in contact with an adherend that can function as a reflective layer.
  • the resistance film, the dielectric layer, the characteristics of the present invention, and other configurations are the same as those described for the ⁇ / 4 type radio wave absorber of the present invention.
  • the ⁇ / 4 type radio wave absorber of the present invention has a performance of absorbing unnecessary electromagnetic waves, it is suitable as a radio wave countermeasure member in, for example, an optical transceiver, a next-generation mobile communication system (5G), a short-range wireless transfer technology, and the like. Available. In addition, it should also be used for the purpose of suppressing radio wave interference and reducing noise in intelligent transportation systems (ITS) that communicate information between automobiles, roads, and people, and millimeter-wave radars used in automobile collision prevention systems. Can be done.
  • ITS intelligent transportation systems
  • the present invention relates to a millimeter wave radar including the ⁇ / 4 type radio absorber of the present invention in one aspect thereof.
  • the frequency of the radio wave targeted by the ⁇ / 4 type radio wave absorber of the present invention is preferably 10 to 150 GHz, more preferably 50 to 100 GHz, and even more preferably 70 to 90 GHz.
  • dielectric layer material 85 parts by weight of 2-ethylhexyl acrylate, 15 parts by weight of butyl acrylate, 10 parts by weight of acrylic acid, 0.15 parts by weight of 2,2-dimethoxy-2-phenylacetophenone, and 0.15 parts by weight of hexanediol diacrylate are uniformly mixed.
  • a polymerizable composition Nitrogen was purged into this polymerizable composition to remove dissolved oxygen. Then, the release-treated 50 ⁇ m-thick PET film was coated on the release-treated surface, and the release-treated 50 ⁇ m-thick PET film was further coated on the release-treated surface of the 50 ⁇ m-thick PET film formed by the above coating.
  • the chemical lamp is superposed on the PET film that has been mold-released so that the thickness of the adhesive layer is 0.5 mm, and the UV irradiation intensity of the PET film on the coating side is 5 mW / cm 2 .
  • the lamp intensity was adjusted and the film was irradiated with ultraviolet rays for 15 minutes to obtain an adhesive tape having an adhesive layer thickness of 0.5 mm.
  • the chemical lamp is superposed on the PET film that has been mold-released so that the thickness of the adhesive layer is 0.5 mm, and the UV irradiation intensity of the PET film on the coating side is 5 mW / cm 2 .
  • the lamp intensity was adjusted and the film was irradiated with ultraviolet rays for 15 minutes to obtain an adhesive tape having an adhesive layer thickness of 0.5 mm.
  • the release-treated 50 ⁇ m-thick PET film was coated on the release-treated surface, and the release-treated 50 ⁇ m-thick PET film was further coated on the release-treated surface of the 50 ⁇ m-thick PET film formed by the above coating.
  • the chemical lamp is superposed on the PET film that has been mold-released so that the thickness of the adhesive layer is 0.5 mm, and the UV irradiation intensity of the PET film on the coating side is 5 mW / cm 2 .
  • the lamp intensity was adjusted and irradiated with ultraviolet rays for 15 minutes to obtain an adhesive tape having an adhesive layer thickness of 0.4 mm.
  • the release-treated 50 ⁇ m-thick PET film was coated on the release-treated surface, and the release-treated 50 ⁇ m-thick PET film was further coated on the release-treated surface of the 50 ⁇ m-thick PET film formed by the above coating.
  • the chemical lamp is superposed on the PET film that has been mold-released so that the thickness of the adhesive layer is 0.5 mm, and the UV irradiation intensity of the PET film on the coating side is 5 mW / cm 2 .
  • the lamp intensity was adjusted and irradiated with ultraviolet rays for 15 minutes to obtain an adhesive tape having an adhesive layer thickness of 1.1 mm.
  • the release-treated 50 ⁇ m-thick PET film was coated on the release-treated surface, and the release-treated 50 ⁇ m-thick PET film was further coated on the release-treated surface of the 50 ⁇ m-thick PET film formed by the above coating.
  • the chemical lamp is superposed on the PET film that has been mold-released so that the thickness of the adhesive layer is 0.5 mm, and the UV irradiation intensity of the PET film on the coating side is 5 mW / cm 2 .
  • the lamp intensity was adjusted and the film was irradiated with ultraviolet rays for 15 minutes to obtain an adhesive tape having a thickness of the adhesive layer of 1.8 mm.
  • the release-treated 50 ⁇ m-thick PET film was coated on the release-treated surface, and the release-treated 50 ⁇ m-thick PET film was further coated on the release-treated surface of the 50 ⁇ m-thick PET film formed by the above coating.
  • the chemical lamp is superposed on the PET film that has been mold-released so that the thickness of the adhesive layer is 0.5 mm, and the UV irradiation intensity of the PET film on the coating side is 5 mW / cm 2 .
  • the lamp intensity was adjusted and the film was irradiated with ultraviolet rays for 15 minutes to obtain an adhesive tape having an adhesive layer thickness of 1.7 mm.
  • the release-treated 50 ⁇ m-thick PET film was coated on the release-treated surface, and the release-treated 50 ⁇ m-thick PET film was further coated on the release-treated surface of the 50 ⁇ m-thick PET film formed by the above coating.
  • the chemical lamp is superposed on the PET film that has been mold-released so that the thickness of the adhesive layer is 0.5 mm, and the UV irradiation intensity of the PET film on the coating side is 5 mW / cm 2 .
  • the lamp intensity was adjusted and the film was irradiated with ultraviolet rays for 15 minutes to obtain an adhesive tape having an adhesive layer thickness of 1.1 mm.
  • ⁇ / 4 type radio wave absorber (Example 1) As a support, a polyester film having a thickness of 125 ⁇ m (relative permittivity 3.3, glass transition temperature Tg 80 ° C., heat shrinkage rate 0.25% at 100 ° C.) (diafoil manufactured by Mitsubishi Chemical Corporation) was prepared. A resistance film having a thickness of 11.1 nm and a sheet resistance value of 341 ⁇ / ⁇ was formed on the PET film by DC sputtering. Sputtering was carried out using Hastelloy C-276 as a target, introduced at an output of 0.4 kW and an Ar gas flow rate of 100 sccm, and adjusted to a pressure of 0.12 Pa.
  • Hastelloy C-276 as a target, introduced at an output of 0.4 kW and an Ar gas flow rate of 100 sccm, and adjusted to a pressure of 0.12 Pa.
  • a dielectric material made of an acrylic double-sided adhesive tape having a thickness of 0.5 mm (reference example 1: relative permittivity 3.1, glass transition temperature Tg 0 ° C.) was laminated on the formed resistance film, and further thickened on the dielectric material.
  • a reflective layer (copper foil, Ra 0.3 nm) made of 30 ⁇ m copper was laminated to obtain a ⁇ / 4 type radio wave absorber.
  • Example 2 A ⁇ / 4 type radio wave absorber was obtained in the same manner as in Example 1 except that the resistance film had a thickness of 11.0 nm, the sheet resistance value was 345 ⁇ / ⁇ , and the acrylic double-sided adhesive tape of Reference Example 2 was used as the dielectric. It was.
  • Example 3 A ⁇ / 4 type radio wave absorber was obtained in the same manner as in Example 1 except that the resistance film had a thickness of 10.8 nm, the sheet resistance value was 353 ⁇ / ⁇ , and the acrylic double-sided adhesive tape of Reference Example 3 was used as the dielectric. It was.
  • Example 4 As a support, a polypropylene film having a thickness of 200 ⁇ m (relative permittivity 2.9, glass transition temperature Tg 0 ° C., heat shrinkage rate 0.4% at 100 ° C.) (PP craft film manufactured by Acrysandy Co., Ltd.) is used, and a resistance film is used. The thickness is 11.0 nm, the sheet resistance value is 345 ⁇ / ⁇ , and the polyethylene-heated foam sheet-like high foam (thickness 0.6 mm) of Reference Example 4 is used as a dielectric, and adhesive tapes (acrylic double-sided adhesive tape, thickness) are used on both sides thereof.
  • a ⁇ / 4 type radio absorber was obtained in the same manner as in Example 1 except that the film was laminated via 30 ⁇ m and a relative permittivity of 3.0).
  • Example 5 A ⁇ / 4 type radio wave absorber was obtained in the same manner as in Example 1 except that the resistance film had a thickness of 10.9 nm, the sheet resistance value was 352 ⁇ / ⁇ , and the acrylic double-sided adhesive tape of Reference Example 5 was used as the dielectric. It was.
  • Example 6 As a support, a polylactic acid film having a thickness of 125 ⁇ m (relative permittivity 2.6, glass transition temperature Tg 40 ° C., heat shrinkage rate 0.4% at 100 ° C.) (manufactured by Mitsubishi Chemical Corporation) is used, and the resistance film is thickened.
  • a ⁇ / 4 type radio wave absorber was obtained in the same manner as in Example 1 except that the thickness was 12 nm and the sheet resistance value was 351 ⁇ / ⁇ .
  • Example 1 A ⁇ / 4 type radio wave absorber was obtained in the same manner as in Example 1 except that the resistance film had a thickness of 10.5 nm, the sheet resistance value was 360 ⁇ / ⁇ , and the acrylic double-sided adhesive tape of Reference Example 6 was used as the dielectric. It was.
  • Example 2 A ⁇ / 4 type radio wave absorber was obtained in the same manner as in Example 1 except that the resistance film had a thickness of 10.7 nm, the sheet resistance value was 353 ⁇ / ⁇ , and the acrylic double-sided adhesive tape of Reference Example 7 was used as the dielectric. It was.
  • Example 3 A 125 ⁇ m-thick polyurethane film (relative permittivity 5.6, glass transition temperature Tg-20 ° C, heat shrinkage 0.9% at 100 ° C) (polyurethane film manufactured by Nippon Unipolymer Co., Ltd.) was used as the support.
  • a ⁇ / 4 type radio wave absorber is used in the same manner as in Example 1 except that the resistance film has a thickness of 10.8 nm, the sheet resistance value is 350 ⁇ / ⁇ , and the acrylic double-sided adhesive tape of Reference Example 8 is used as the dielectric. Obtained.

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Abstract

The present invention addresses the problem of providing a λ/4 radiowave absorber that exhibits at least a certain radiowave absorption performance from low temperature to high temperature (particularly high temperatures of 100℃ or more). The problem is solved by a λ/4 radiowave absorber of which the minimum value of the amount of radiowave absorption at 79 GHz is 10 dB or more at 60 to 130℃.

Description

λ／４型電波吸収体λ / 4 type radio wave absorber
　本発明は、λ／４型電波吸収体等に関する。 The present invention relates to a λ / 4 type radio wave absorber and the like.
　近年、携帯電話やスマートフォン等の携帯通信機器の普及が急速に進んでおり、また自動車等において多くの電子機器が搭載されるようになり、これらから発生する電波・ノイズを原因とする電波障害、他の電子機器の誤動作等の問題が多発している。このような電波障害、誤動作等を防止する方策として、各種の電波吸収体が検討されている。例えば、特許文献１には、６０～９０ＧＨｚの周波数帯域において、電磁波吸収量が２０ｄＢ以上である周波数帯域の帯域幅が２ＧＨｚ以上である電磁波吸収体が開示されている。 In recent years, mobile communication devices such as mobile phones and smartphones have rapidly become widespread, and many electronic devices have come to be installed in automobiles, etc., and radio interference caused by radio waves and noise generated from these devices, Problems such as malfunctions of other electronic devices frequently occur. Various radio wave absorbers are being studied as measures to prevent such radio interference and malfunction. For example, Patent Document 1 discloses an electromagnetic wave absorber having a bandwidth of 2 GHz or more in a frequency band having an electromagnetic wave absorption amount of 20 dB or more in a frequency band of 60 to 90 GHz.
特開第２０１８－０９８３６７号公報JP-A-2018-098367
　通信技術や自動運転技術において高周波数領域の電波に関して広周波数範囲において高く吸収する電波吸収体の需要が高まっている。本発明者は、研究を進める中で、これらの電波吸収体は、自動車等に搭載されるデバイス用の部品として用いられるため、温度の激しい変化に対応できる温冷耐久性が必要である点に着目した。 In communication technology and automatic driving technology, there is an increasing demand for radio absorbers that absorb high frequency radio waves in a wide frequency range. In the course of research by the present inventor, since these radio wave absorbers are used as parts for devices mounted on automobiles and the like, they need to have thermal and cooling durability that can cope with drastic changes in temperature. I paid attention to it.
　そこで、本発明は、低温から高温（特に１００℃以上の高温）において一定以上の電波吸収性を発揮できるλ／４型電波吸収体を提供することを課題とする。 Therefore, an object of the present invention is to provide a λ / 4 type radio wave absorber that can exhibit a certain level of radio wave absorption from a low temperature to a high temperature (particularly, a high temperature of 100 ° C. or higher).
　本発明者は、上記課題に鑑みて鋭意研究を進めた結果、６０～１３０℃における７９ＧＨｚでの電波吸収量の最小値が１０ｄＢ以上である、λ／４型電波吸収体、であれば、上記課題を解決できることを見出した。本発明者はこの知見に基づいてさらに研究を進めた結果、本発明を完成させた。 As a result of diligent research in view of the above problems, the present inventor considers a λ / 4 type radio wave absorber having a minimum value of radio wave absorption at 79 GHz at 60 to 130 ° C. of 10 dB or more. I found that I could solve the problem. The present inventor has completed the present invention as a result of further research based on this finding.
　即ち、本発明は、下記の態様を包含する。 That is, the present invention includes the following aspects.
　項１．　６０～１３０℃における７９ＧＨｚでの電波吸収量の最小値が１０ｄＢ以上である、λ／４型電波吸収体。 Item 1. A λ / 4 type radio wave absorber in which the minimum value of the radio wave absorption amount at 79 GHz at 60 to 130 ° C. is 10 dB or more.
　項２．　誘電体層を含み、前記誘電体層のガラス転移温度Ｔｇが－１０℃以上である、項１に記載のλ／４型電波吸収体。 Item 2. Item 2. The λ / 4 type radio wave absorber according to Item 1, which includes a dielectric layer and has a glass transition temperature Tg of the dielectric layer of −10 ° C. or higher.
　項３．　誘電体層を含み、前記誘電体層の比誘電率が１～５である、項１又は２に記載のλ／４型電波吸収体。 Item 3. Item 2. The λ / 4 type radio wave absorber according to Item 1 or 2, which includes a dielectric layer and has a relative permittivity of 1 to 5 of the dielectric layer.
　項４．　支持体を含み、前記支持体のガラス転移温度Ｔｇが４０℃以上である、項１～３のいずれかに記載のλ／４型電波吸収体。 Item 4. Item 2. The λ / 4 type radio wave absorber according to any one of Items 1 to 3, which includes a support and has a glass transition temperature Tg of the support of 40 ° C. or higher.
　項５．　前記支持体の１５０℃、６０分加熱後のＭＤ方向及びＴＤ方向ともに加熱収縮率の絶対値が０．５％以下である、項４に記載のλ／４型電波吸収体。 Item 5. Item 4. The λ / 4 type radio wave absorber according to Item 4, wherein the absolute value of the heat shrinkage rate is 0.5% or less in both the MD direction and the TD direction after heating the support at 150 ° C. for 60 minutes.
　項６．　支持体を含み、前記支持体の比誘電率が１～５である、項１～５のいずれかに記載のλ／４型電波吸収体。 Item 6. Item 2. The λ / 4 type radio wave absorber according to any one of Items 1 to 5, which includes a support and has a relative permittivity of 1 to 5 of the support.
　項７．　項１～６のいずれかに記載のλ／４型電波吸収体を含む、ミリ波レーダー。 Item 7. A millimeter-wave radar including the λ / 4 type radio wave absorber according to any one of Items 1 to 6.
　項８．　抵抗膜及び誘電体層を含み、厚さ３０μｍの銅からなる反射層を誘電体層の他方の面に積層した際の、６０～１３０℃における７９ＧＨｚでの電波吸収量の最小値が１０ｄＢ以上である、λ／４型電波吸収体用部材。 Item 8. When a reflective layer made of copper with a thickness of 30 μm including a resistance film and a dielectric layer is laminated on the other surface of the dielectric layer, the minimum value of the radio wave absorption at 79 GHz at 60 to 130 ° C. is 10 dB or more. There is a member for λ / 4 type radio wave absorber.
　本発明によれば、低温から高温（特に１００℃以上の高温）において一定以上の電波吸収性を発揮できるλ／４型電波吸収体を提供することができる。 According to the present invention, it is possible to provide a λ / 4 type radio wave absorber that can exhibit a certain level of radio wave absorption or higher from a low temperature to a high temperature (particularly, a high temperature of 100 ° C. or higher).
本発明の電波吸収体の一例を示す概略断面図である。It is the schematic sectional drawing which shows an example of the radio wave absorber of this invention. 上方の図は、本発明の電波吸収体用部材の一例を示す概略断面図である。下方は、該部材が接するように配置される、反射層として機能し得る被着体の一例を示す概略断面図である。The upper figure is a schematic cross-sectional view showing an example of a member for a radio wave absorber of the present invention. The lower part is a schematic cross-sectional view showing an example of an adherend that can function as a reflective layer and is arranged so that the members are in contact with each other. 本発明の電波吸収体の用途の一例（粘着剤を介して筐体上に配置されてなる形態の一例）を示す概略断面図である。It is a schematic cross-sectional view which shows an example of application of the radio wave absorber of this invention (an example of the form which is arranged on the housing through the adhesive).
　本明細書中において、「含有」及び「含む」なる表現については、「含有」、「含む」、「実質的にからなる」及び「のみからなる」という概念を含む。 In the present specification, the expressions "contains" and "includes" include the concepts of "contains", "includes", "substantially consists" and "consists of only".
　本発明は、その一態様において、６０～１３０℃における７９ＧＨｚでの電波吸収量の最小値が１０ｄＢ以上である、λ／４型電波吸収体（本明細書において、「本発明のλ／４型電波吸収体」と示すこともある。）、に関する。以下に、これについて説明する。 In one aspect of the present invention, a λ / 4 type radio wave absorber having a minimum value of radio wave absorption at 79 GHz at 60 to 130 ° C. of 10 dB or more (in the present specification, "λ / 4 type of the present invention". Sometimes referred to as "radio wave absorber"). This will be described below.
　＜１．特性＞
　本発明のλ／４型電波吸収体は、６０～１３０℃における７９ＧＨｚでの電波吸収量の最小値が１０ｄＢ以上である、という特性（本明細書において、「本発明の特性」と示すこともある。）を備える。この特性を備えることにより、高温（特に１００℃以上の高温）域のみならず、低温から高温の広い温度域において一定以上の電波吸収性を発揮することができる。 <1. Characteristics>
The λ / 4 type radio wave absorber of the present invention has a characteristic that the minimum value of the radio wave absorption amount at 79 GHz at 60 to 130 ° C. is 10 dB or more (also referred to as “characteristic of the present invention” in the present specification. There is.) By having this characteristic, it is possible to exhibit a certain level of radio wave absorption not only in a high temperature range (particularly, a high temperature of 100 ° C. or higher) but also in a wide temperature range from low temperature to high temperature.
　上記電波吸収量の最小値は、好ましくは１０ｄＢ以上、より好ましくは１５ｄＢ以上である。上記電波吸収量の上限は特に制限されず、特に制限されず、例えば４０ｄＢ、３０ｄＢ、２５ｄＢである。 The minimum value of the radio wave absorption amount is preferably 10 dB or more, more preferably 15 dB or more. The upper limit of the radio wave absorption amount is not particularly limited, and is not particularly limited, for example, 40 dB, 30 dB, and 25 dB.
　本発明の特性は、次のように測定することができる。ネットワークアナライザー　ＭＳ４６４７Ｂ（アンリツ社製）、フリースペース材料測定置　ＢＤ１－２６．Ａ（キーコム社製）を用いて電波吸収測定装置を構成する。この電波吸収測定装置を用いて、得られたλ／４型電波電磁波吸収体の７９ＧＨｚでの電波吸収量をＪＩＳ　Ｒ１６７９に基づいて測定することができる。なお、λ／４型電波吸収体は、電波入射方向が垂直入射となるようにセットする。電波吸収量測定時は、電波が入射する面とは反対の面からポリイミドヒーター等で加熱を行い電波吸収体の温度の調節を行う。電波吸収体の温度は赤外線放射温度計（ＡＤ－５６１３Ａ（エー・アンド・デイ社製）又はその同等品）を用いて測定することができる。 The characteristics of the present invention can be measured as follows. Network analyzer MS4647B (manufactured by Anritsu), free space material measurement device BD1-26. A radio wave absorption measuring device is configured using A (manufactured by Keycom). Using this radio wave absorption measuring device, the radio wave absorption amount of the obtained λ / 4 type radio wave electromagnetic wave absorber at 79 GHz can be measured based on JIS R1679. The λ / 4 type radio wave absorber is set so that the radio wave incident direction is vertical incident. When measuring the amount of radio wave absorption, the temperature of the radio wave absorber is adjusted by heating with a polyimide heater or the like from the surface opposite to the surface on which the radio wave is incident. The temperature of the radio wave absorber can be measured using an infrared radiation thermometer (AD-5613A (manufactured by A & D Co., Ltd.) or an equivalent product thereof).
　＜２．構成＞
　本発明のλ／４型電波吸収体の構成は、上記本発明の特性を備えるものである限り特に制限されず、例えば電波吸収体の公知の構成を採用することができる。一実施形態において、本発明のλ／４型電波吸収体は、抵抗膜、誘電体層、及び反射層を有する、という構成を備える。好ましい一実施形態において、本発明のλ／４型電波吸収体は、支持体、抵抗膜、誘電体層、及び反射層を有する、という構成を備える。以下に、これらの実施形態について説明する。 <2. Configuration>
The configuration of the λ / 4 type radio wave absorber of the present invention is not particularly limited as long as it has the above-mentioned characteristics of the present invention, and for example, a known configuration of the radio wave absorber can be adopted. In one embodiment, the λ / 4 type radio wave absorber of the present invention has a configuration having a resistance film, a dielectric layer, and a reflection layer. In a preferred embodiment, the λ / 4 type radio wave absorber of the present invention includes a support, a resistance film, a dielectric layer, and a reflection layer. Hereinafter, these embodiments will be described.
　＜２－１．支持体＞
　本発明のλ／４型電波吸収体が抵抗膜を有する場合、さらに支持体を有することが好ましい。これにより、抵抗膜を保護することができ、電波吸収体としての耐久性を高めることが可能である。支持体は、シート状のものである限り、特に制限されない。支持体としては、特に制限されないが、例えば樹脂基材が挙げられる。 <2-1. Support>
When the λ / 4 type radio wave absorber of the present invention has a resistance film, it is preferable to further have a support. As a result, the resistance film can be protected and the durability as a radio wave absorber can be enhanced. The support is not particularly limited as long as it is in the form of a sheet. The support is not particularly limited, and examples thereof include a resin base material.
　樹脂基材は、樹脂を素材として含む基材であって、シート状のものである限り、特に制限されない。樹脂基材は、本発明の効果が著しく損なわれない限りにおいて、樹脂以外の成分が含まれていてもよい。例えば、比誘電率等を調整する観点から酸化チタン等が含まれていてもよい。樹脂基材中の樹脂の合計量は、例えば８０質量％以上、好ましくは９０質量％以上、より好ましくは９５質量％以上、さらに好ましくは９９質量％以上であり、通常１００質量％未満である。 The resin base material is a base material containing resin as a material, and is not particularly limited as long as it is in the form of a sheet. The resin base material may contain components other than the resin as long as the effects of the present invention are not significantly impaired. For example, titanium oxide or the like may be contained from the viewpoint of adjusting the relative permittivity or the like. The total amount of the resin in the resin base material is, for example, 80% by mass or more, preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably 99% by mass or more, and usually less than 100% by mass.
　樹脂としては、特に制限されず、例えばポリエチレンテレフタレート（ＰＥＴ）、ポリエチレンナフタレート、変性ポリエステル等のポリエステル系樹脂、ポリエチレン（ＰＥ）樹脂、ポリプロピレン（ＰＰ）樹脂、ポリスチレン樹脂、環状オレフィン系樹脂等のポリオレフィン類樹脂、ポリ塩化ビニル、ポリ塩化ビニリデン、ポリフッ化ビニリデン等のビニル系樹脂、ポリビニルブチラール（ＰＶＢ）等のポリビニルアセタール樹脂、ポリエーテルエーテルケトン（ＰＥＥＫ）樹脂、ポリサルホン（ＰＳＦ）樹脂、ポリエーテルサルホン（ＰＥＳ）樹脂、ポリカーボネート（ＰＣ）樹脂、ポリアミド樹脂、ポリイミド樹脂、アクリル樹脂、トリアセチルセルロース（ＴＡＣ）樹脂等が挙げられる。これらは１種単独でまたは２種以上の組合せで使用することができる。 The resin is not particularly limited, and is, for example, a polyester resin such as polyethylene terephthalate (PET), polyethylene naphthalate, or modified polyester, a polyolefin such as a polyethylene (PE) resin, a polypropylene (PP) resin, a polystyrene resin, or a cyclic olefin resin. Similar resins, vinyl-based resins such as polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, polyvinyl acetal resin such as polyvinyl butyral (PVB), polyether ether ketone (PEEK) resin, polysalphon (PSF) resin, polyether salphon Examples thereof include (PES) resin, polycarbonate (PC) resin, polyamide resin, polyimide resin, acrylic resin, and triacetyl cellulose (TAC) resin. These can be used alone or in combination of two or more.
　これらの中でも、生産性や強度の観点、本発明の特性の観点等から、好ましくはポリエステル系樹脂、より好ましくはポリエチレンテレフタレートが挙げられる。 Among these, polyester-based resins are preferable, and polyethylene terephthalate is more preferable, from the viewpoints of productivity and strength, the characteristics of the present invention, and the like.
　支持体の比誘電率は、特に制限されない。支持体の比誘電率は、例えば１～２０、好ましくは１～１５、より好ましくは１～１０である。中でも、誘電率の温度変化をより低く抑えることができるという観点から、支持体の比誘電率は、特に好ましくは１～５である。 The relative permittivity of the support is not particularly limited. The relative permittivity of the support is, for example, 1 to 20, preferably 1 to 15, and more preferably 1 to 10. Above all, the relative permittivity of the support is particularly preferably 1 to 5 from the viewpoint that the temperature change of the permittivity can be suppressed to a lower level.
　支持体の比誘電率は、後述の誘電体層の比誘電率と同様にして測定することができる。 The specific dielectric constant of the support can be measured in the same manner as the specific dielectric constant of the dielectric layer described later.
　支持体のガラス転移温度Ｔｇは、本発明の特性を満たし得るものである限り特に制限されない。支持体のガラス転移温度Ｔｇは、本発明の特性の観点から、好ましくは２０℃以上、より好ましくは３０℃以上、さらに好ましくは４０℃以上、よりさらに好ましくは５０℃以上、とりわけさらに好ましくは６０℃以上、特に好ましくは７０℃以上である。該温度の上限は、特に制限されず、例えば２５０℃、２００℃、１５０℃である。 The glass transition temperature Tg of the support is not particularly limited as long as it can satisfy the characteristics of the present invention. From the viewpoint of the characteristics of the present invention, the glass transition temperature Tg of the support is preferably 20 ° C. or higher, more preferably 30 ° C. or higher, still more preferably 40 ° C. or higher, still more preferably 50 ° C. or higher, and particularly preferably 60 ° C. or higher. ° C. or higher, particularly preferably 70 ° C. or higher. The upper limit of the temperature is not particularly limited, and is, for example, 250 ° C, 200 ° C, and 150 ° C.
　支持体の加熱収縮率は本発明の特性を満たし得るものである限り特に制限されない。支持体の加熱収縮率の絶対値はＭＤ方向およびＴＤ方向共に、本発明の特性の観点から、好ましくは０．５％以下、より好ましくは０．４％以下、さらに好ましくは０．３％以下である。該収縮率の下限は、特に制限されず、例えば０％、０．０１％、０．１％である。 The heat shrinkage rate of the support is not particularly limited as long as it can satisfy the characteristics of the present invention. The absolute value of the heat shrinkage of the support is preferably 0.5% or less, more preferably 0.4% or less, still more preferably 0.3% or less from the viewpoint of the characteristics of the present invention in both the MD direction and the TD direction. Is. The lower limit of the shrinkage rate is not particularly limited, and is, for example, 0%, 0.01%, and 0.1%.
　支持体の加熱収縮率はＪＩＳＺ１７１５：２００９に基づいて測定することができる。具体的には、支持体をＭＤ方向およびＴＤ方向にそれぞれ２０ｍｍ×１５０ｍｍに切断した後、試験片の長さ方向の中央部に５０ｍｍ間隔の標線を付ける。１５０℃、６０分加熱し、取り出し後、室温に３０分間放置してから標線間距離を測定して下式からＭＤ方向およびＴＤ方向の加熱収縮率を求めることができる（ＪＩＳＺ１７１５：２００９）。加熱収縮率が負の値であるときは、加熱後に膨張したことを意味する。
　　　　　　　　　　Ｓ＝（Ｌ１－Ｌ２）×１００／Ｌ１
ここで、Ｓ：加熱収縮率（％）、Ｌ１：加熱前の標線間距離、Ｌ２：加熱後の標線間距離を表す。 The heat shrinkage of the support can be measured based on JISZ1715: 2009. Specifically, after cutting the support into 20 mm × 150 mm in the MD direction and the TD direction, respectively, a marked line at intervals of 50 mm is attached to the central portion in the length direction of the test piece. The heat shrinkage rate in the MD direction and the TD direction can be obtained from the following formula by measuring the distance between the marked lines after heating at 150 ° C. for 60 minutes and leaving the mixture at room temperature for 30 minutes (JISZ1715: 2009). When the heat shrinkage rate is a negative value, it means that the material has expanded after heating.
S = (L1-L2) x 100 / L1
Here, S: the heating shrinkage rate (%), L1: the distance between the marked lines before heating, and L2: the distance between the marked lines after heating.
　上記加熱収縮率を調整する方法は特に制限されないが、例えば、上記加熱収縮率を満たす樹脂シートを支持体として用いる方法、支持体に延伸処理、熱アニール処理、事前の熱収縮処理等を行う方法等により調整することができる。 The method for adjusting the heat shrinkage rate is not particularly limited, and for example, a method using a resin sheet satisfying the heat shrinkage rate as a support, a method of performing a stretching treatment, a heat annealing treatment, a prior heat shrinkage treatment, or the like on the support. It can be adjusted by such means.
　支持体の厚みは、特に制限されない。支持体の厚みは、例えば５μｍ以上５００μｍ以下、好ましくは１０μｍ以上３００μｍ以下、より好ましくは２０μｍ以上３００μｍ以下である。特に、本発明の特性の観点から、支持体の厚みは、好ましくは３０μｍ以上２５０μｍ以下、より好ましくは４０μｍ以上２００μｍ以下である。 The thickness of the support is not particularly limited. The thickness of the support is, for example, 5 μm or more and 500 μm or less, preferably 10 μm or more and 300 μm or less, and more preferably 20 μm or more and 300 μm or less. In particular, from the viewpoint of the characteristics of the present invention, the thickness of the support is preferably 30 μm or more and 250 μm or less, and more preferably 40 μm or more and 200 μm or less.
　支持体の層構成は特に制限されない。支持体は、１種単独の支持体から構成されるものであってもよいし、２種以上の支持体が複数組み合わされたものであってもよい。 The layer structure of the support is not particularly limited. The support may be composed of one type of support alone, or may be a combination of two or more types of supports.
　＜２－２．抵抗膜＞
　抵抗膜は、電波吸収体において抵抗層として機能し得る層を含む限り特に制限されない。 <2-2. Resistance film>
The resistance film is not particularly limited as long as it includes a layer that can function as a resistance layer in the radio wave absorber.
　抵抗膜の抵抗値は、特に制限されない。抵抗膜の抵抗値は、例えば２００～６００Ω／□である。該範囲の中でも、より好ましくは２２０～５５０Ω／□、さらに好ましくは２５０～５００Ω／□である。 The resistance value of the resistance film is not particularly limited. The resistance value of the resistance film is, for example, 200 to 600 Ω / □. Within this range, it is more preferably 220 to 550 Ω / □, and even more preferably 250 to 500 Ω / □.
　抵抗膜の抵抗値は、表面抵抗計（ＭＩＴＳＵＢＩＳＨＩ ＣＨＥＭＩＣＡＬＡＮＡＬＹＴＥＣＨ社製、商品名「Ｌｏｒｅｓｔａ－ＥＰ」）を用いて、４端子法により測定することができる。また、抵抗値は、誘電体及び支持体等が積層され抵抗膜を直接測定できない場合は、非接触抵抗計（製品名「ＥＣ－８０Ｐ、ナプソン社製、又はその同等品）を用いて渦電流法により、支持体の抵抗膜とは逆の表面から測定することができる。 The resistance value of the resistance film can be measured by the 4-terminal method using a surface resistance meter (manufactured by MITSUBISHI CHEMICALANALYTECH, trade name "Loresta-EP"). For the resistance value, use a non-contact resistance meter (product name "EC-80P, manufactured by Napson, or an equivalent product) if the dielectric and support are laminated and the resistance film cannot be measured directly. By the method, it is possible to measure from the surface opposite to the resistance film of the support.
　抵抗膜の厚みは、特に制限されない。抵抗膜の厚みは、例えば１ｎｍ以上２００ｎｍ以下、好ましくは２ｎｍ以上１００ｎｍ以下、より好ましくは２ｎｍ以上５０ｎｍ以下である。 The thickness of the resistance film is not particularly limited. The thickness of the resistance film is, for example, 1 nm or more and 200 nm or less, preferably 2 nm or more and 100 nm or less, and more preferably 2 nm or more and 50 nm or less.
　抵抗膜の層構成は特に制限されない。抵抗膜は、１種単独の層から構成されるものであってもよいし、２種以上の層が複数組み合わされたものであってもよい。 The layer structure of the resistance film is not particularly limited. The resistance film may be composed of a single layer of one type, or may be a combination of a plurality of layers of two or more types.
　＜２－２－１．抵抗層＞
　＜２－２－１－１．ＩＴＯ含有抵抗層＞
　抵抗層としては、例えば酸化インジウムスズ（以下「ＩＴＯ」とする）が用いられる。なかでも、非晶質構造が極めて安定であり、高温多湿の環境下においても抵抗層のシート抵抗の変動を抑えることができる点から、１～４０重量％のＳｎＯ２、より好ましくは２～３５重量％のＳｎＯ２を含有するＩＴＯを含有するものが好ましく用いられる。上記ＩＴＯの含有量は抵抗層中、例えば５０質量％以上、好ましくは７０質量％以上、より好ましくは９０質量％以上、さらに好ましくは９５質量％以上であり、通常１００質量％未満である。 <2-2-1. Resistance layer>
<2-2-1-1. ITO-containing resistance layer>
As the resistance layer, for example, indium tin oxide (hereinafter referred to as "ITO") is used. Among them, SnO 2 of 1 to 40% by weight, more preferably 2 to 35, because the amorphous structure is extremely stable and the fluctuation of the sheet resistance of the resistance layer can be suppressed even in a high temperature and high humidity environment. Those containing ITO containing% by weight SnO 2 are preferably used. The content of ITO in the resistance layer is, for example, 50% by mass or more, preferably 70% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and usually less than 100% by mass.
　＜２－２－１－２．モリブデン含有抵抗層＞
　抵抗層としては、耐久性、シート抵抗の調整が容易である観点から、モリブデンを含有する抵抗層が好ましく用いられる。モリブデンの含有量の下限は特に限定されないが、より耐久性を高める観点から、５重量％が好ましく、７重量％がより好ましく、９重量％が更に好ましく、１１重量％がより更に好ましく、１３重量％が特に好ましく、１５重量％が非常に好ましく、１６重量％が最も好ましい。また、上記モリブデンの含有量の上限は、表面抵抗値の調整の容易化の観点から、７０重量％が好ましく、３０重量％がより好ましく、２５重量％がさらに好ましく、２０重量％が更により好ましい。 <2-2-1-2. Molybdenum-containing resistance layer>
As the resistance layer, a resistance layer containing molybdenum is preferably used from the viewpoint of durability and easy adjustment of sheet resistance. The lower limit of the molybdenum content is not particularly limited, but from the viewpoint of further enhancing durability, 5% by weight is preferable, 7% by weight is more preferable, 9% by weight is further preferable, 11% by weight is further preferable, and 13% by weight is used. % Is particularly preferred, 15% by weight is very preferred, and 16% by weight is most preferred. The upper limit of the molybdenum content is preferably 70% by weight, more preferably 30% by weight, further preferably 25% by weight, still more preferably 20% by weight, from the viewpoint of facilitating adjustment of the surface resistance value. ..
　上記抵抗層は、モリブデンを含有している場合、さらにニッケル及びクロムを含有することがより好ましい。抵抗層にモリブデンに加えてニッケル及びクロムを含有することでより耐久性に優れた電波吸収体とすることができる。ニッケル、クロム及びモリブデンを含有する合金としては、例えば、ハステロイＢ－２、Ｂ－３、Ｃ－４、Ｃ－２０００、Ｃ－２２、Ｃ－２７６、Ｇ－３０、Ｎ、Ｗ、Ｘ等の各種グレードが挙げられる。 When the resistance layer contains molybdenum, it is more preferable that it further contains nickel and chromium. By containing nickel and chromium in addition to molybdenum in the resistance layer, a more durable radio wave absorber can be obtained. Examples of alloys containing nickel, chromium and molybdenum include Hasteroy B-2, B-3, C-4, C-2000, C-22, C-276, G-30, N, W and X. Various grades can be mentioned.
　上記抵抗層がモリブデン、ニッケル及びクロムを含有する場合、モリブデンの含有量が５重量％以上、ニッケルの含有量が４０重量％以上、クロムの含有量が１重量％以上であることが好ましい。モリブデン、ニッケル及びクロムの含有量が上記範囲であることで、より耐久性に優れた電波吸収体とすることができる。上記モリブデン、ニッケル及びクロムの含有量は、モリブデン含有量が７重量％以上、ニッケル含有量が４５重量％以上、クロム含有量が３重量％以上であることがより好ましい。上記モリブデン、ニッケル及びクロムの含有量は、モリブデン含有量が９重量％以上、ニッケル含有量が４７重量％以上、クロム含有量が５重量％以上であることが更に好ましい。上記モリブデン、ニッケル及びクロムの含有量は、モリブデン含有量が１１重量％以上、ニッケル含有量が５０重量％以上、クロム含有量が１０重量％以上であることがより更に好ましい。上記モリブデン、ニッケル及びクロムの含有量は、モリブデン含有量が１３重量％以上、ニッケル含有量が５３重量％以上、クロム含有量が１２重量％以上であることが特に好ましい。上記モリブデン、ニッケル及びクロムの含有量は、モリブデン含有量が１５重量％以上、ニッケル含有量が５５重量％以上、クロム含有量が１５重量％以上であることが非常に好ましい。上記モリブデン、ニッケル及びクロムの含有量は、モリブデン含有量が１６重量％以上、ニッケル含有量が５７重量％以上、クロム含有量が１６重量％以上であることが最も好ましい。また、上記ニッケルの含有量は、８０重量％以下であることが好ましく、７０重量％以下であることがより好ましく、６５重量％以下であることが更に好ましい。上記クロム含有量の上限は、５０重量％以下であることが好ましく、４０重量％以下であることがより好ましく、３５重量％以下であることが更に好ましい。 When the resistance layer contains molybdenum, nickel and chromium, it is preferable that the molybdenum content is 5% by weight or more, the nickel content is 40% by weight or more, and the chromium content is 1% by weight or more. When the contents of molybdenum, nickel and chromium are in the above range, a radio wave absorber having more excellent durability can be obtained. The molybdenum, nickel and chromium contents are more preferably 7% by weight or more, nickel content of 45% by weight or more, and chromium content of 3% by weight or more. The molybdenum, nickel and chromium contents are more preferably 9% by weight or more, the nickel content is 47% by weight or more, and the chromium content is 5% by weight or more. The molybdenum, nickel and chromium contents are more preferably 11% by weight or more, the nickel content is 50% by weight or more, and the chromium content is 10% by weight or more. As for the contents of molybdenum, nickel and chromium, it is particularly preferable that the molybdenum content is 13% by weight or more, the nickel content is 53% by weight or more, and the chromium content is 12% by weight or more. As for the contents of molybdenum, nickel and chromium, it is very preferable that the molybdenum content is 15% by weight or more, the nickel content is 55% by weight or more, and the chromium content is 15% by weight or more. The molybdenum, nickel and chromium contents are most preferably 16% by weight or more, nickel content is 57% by weight or more, and chromium content is 16% by weight or more. The nickel content is preferably 80% by weight or less, more preferably 70% by weight or less, and further preferably 65% by weight or less. The upper limit of the chromium content is preferably 50% by weight or less, more preferably 40% by weight or less, and further preferably 35% by weight or less.
　上記抵抗層は、上記モリブデン、ニッケル及びクロム以外の金属を含有してもよい。そのような金属としては、例えば、鉄、コバルト、タングステン、マンガン、チタン等が挙げられる。上記抵抗層がモリブデン、ニッケル及びクロムを含有する場合、上記モリブデン、ニッケル及びクロム以外の金属の合計含有量の上限は、抵抗層の耐久性の観点から、好ましくは４５重量％、より好ましくは４０重量％、更に好ましくは３５重量％、より更に好ましくは３０重量％、特に好ましくは２５重量％、非常に好ましくは２３重量％である。上記モリブデン、ニッケル及びクロム以外の金属の合計含有量の下限は、例えば１重量％以上である。 The resistance layer may contain a metal other than molybdenum, nickel and chromium. Examples of such metals include iron, cobalt, tungsten, manganese, titanium and the like. When the resistance layer contains molybdenum, nickel and chromium, the upper limit of the total content of metals other than molybdenum, nickel and chromium is preferably 45% by weight, more preferably 40, from the viewpoint of durability of the resistance layer. It is by weight%, more preferably 35% by weight, even more preferably 30% by weight, particularly preferably 25% by weight, and very preferably 23% by weight. The lower limit of the total content of the metals other than molybdenum, nickel and chromium is, for example, 1% by weight or more.
　上記抵抗層が鉄を含有する場合、抵抗層の耐久性の観点から、含有量の好ましい上限は２５重量％、より好ましい上限は２０重量％、更に好ましい上限は１５重量％であり、好ましい下限は１重量％である。上記抵抗層がコバルト及び／又はマンガンを含有する場合、抵抗層の耐久性の観点から、それぞれ独立して、含有量の好ましい上限は５重量％、より好ましい上限は４重量％、更に好ましい上限は３重量％であり、好ましい下限は０．１重量％である。上記抵抗層がタングステンを含有する場合、抵抗層の耐久性の観点から、含有量の好ましい上限は８重量％、より好ましい上限は６重量％、更に好ましい上限は４重量％であり、好ましい下限は１重量％である。 When the resistance layer contains iron, the preferable upper limit of the content is 25% by weight, the more preferable upper limit is 20% by weight, the further preferable upper limit is 15% by weight, and the preferable lower limit is 15% by weight from the viewpoint of the durability of the resistance layer. It is 1% by weight. When the resistance layer contains cobalt and / or manganese, the preferable upper limit of the content is 5% by weight, the more preferable upper limit is 4% by weight, and the further preferable upper limit is independently from the viewpoint of the durability of the resistance layer. It is 3% by weight, and the preferable lower limit is 0.1% by weight. When the resistance layer contains tungsten, the preferable upper limit of the content is 8% by weight, the more preferable upper limit is 6% by weight, the further preferable upper limit is 4% by weight, and the preferable lower limit is 4% by weight from the viewpoint of the durability of the resistance layer. It is 1% by weight.
　上記抵抗層は、ケイ素及び／又は炭素を含有してもよい。抵抗層がケイ素及び／又は炭素を含有する場合、上記ケイ素及び／又は炭素の含有量は、それぞれ独立して、１重量％以下であることが好ましく０．５重量％以下であることがより好ましい。また、抵抗層がケイ素及び／又は炭素を含有する場合、上記ケイ素及び／又は炭素の含有量は、０．０１重量％以上であることが好ましい。 The resistance layer may contain silicon and / or carbon. When the resistance layer contains silicon and / or carbon, the content of silicon and / or carbon is preferably 1% by weight or less, and more preferably 0.5% by weight or less, respectively. .. When the resistance layer contains silicon and / or carbon, the content of the silicon and / or carbon is preferably 0.01% by weight or more.
　抵抗層の抵抗値は、特に制限されない。抵抗層の抵抗値は、例えば２００～６００Ω／□である。該範囲の中でも、より好ましくは２２０～５５０Ω／□、さらに好ましくは２５０～５００Ω／□である。 The resistance value of the resistance layer is not particularly limited. The resistance value of the resistance layer is, for example, 200 to 600 Ω / □. Within this range, it is more preferably 220 to 550 Ω / □, and even more preferably 250 to 500 Ω / □.
　抵抗層の厚みは、特に制限されない。抵抗層の厚みは、例えば１ｎｍ以上２００ｎｍ以下、好ましくは２ｎｍ以上１００ｎｍ以下、より好ましくは２ｎｍ以上５０ｎｍ以下である。 The thickness of the resistance layer is not particularly limited. The thickness of the resistance layer is, for example, 1 nm or more and 200 nm or less, preferably 2 nm or more and 100 nm or less, and more preferably 2 nm or more and 50 nm or less.
　抵抗層の層構成は特に制限されない。抵抗層は、１種単独の抵抗層から構成されるものであってもよいし、２種以上の抵抗層が複数組み合わされたものであってもよい。 The layer structure of the resistance layer is not particularly limited. The resistance layer may be composed of one type of resistance layer alone, or may be a combination of two or more types of resistance layers.
　＜２－２－２．バリア層＞
　耐久性の観点から、抵抗膜はバリア層を含むことが好ましい。バリア層は、抵抗層の少なくとも一方の表面上に配置される。バリア層について以下に詳述する。 <2-2-2. Barrier layer>
From the viewpoint of durability, the resistance film preferably contains a barrier layer. The barrier layer is placed on at least one surface of the resistance layer. The barrier layer will be described in detail below.
　バリア層は、抵抗層を保護し、その劣化を抑えることができる層である限り、特に制限されない。バリア層の素材としては、例えば金属化合物、半金属化合物、好ましくは金属又は半金属の酸化物、窒化物、窒化酸化物等が挙げられる。バリア層は、本発明の効果が著しく損なわれない限りにおいて、上記素材以外の成分が含まれていてもよい。その場合、バリア層中の上記素材量は、例えば８０質量％以上、好ましくは９０質量％以上、より好ましくは９５質量％以上、さらに好ましくは９９質量％以上であり、通常１００質量％未満である。 The barrier layer is not particularly limited as long as it is a layer that can protect the resistance layer and suppress its deterioration. Examples of the material of the barrier layer include metal compounds, metalloid compounds, preferably metal or metalloid oxides, nitrides, nitride oxides and the like. The barrier layer may contain components other than the above materials as long as the effects of the present invention are not significantly impaired. In that case, the amount of the material in the barrier layer is, for example, 80% by mass or more, preferably 90% by mass or more, more preferably 95% by mass or more, further preferably 99% by mass or more, and usually less than 100% by mass. ..
　バリア層が含む金属元素としては、例えばチタン、アルミニウム、ニオブ、コバルト、ニッケル等が挙げられる。バリア層が含む半金属元素としては、例えばケイ素、ゲルマニウム、アンチモン、ビスマス等が挙げられる。 Examples of the metal element contained in the barrier layer include titanium, aluminum, niobium, cobalt, nickel and the like. Examples of the metalloid element contained in the barrier layer include silicon, germanium, antimony, bismuth and the like.
　上記酸化物としては、例えばＭＯＸ［式中、Ｘは式：ｎ／１００≦Ｘ≦ｎ／２（ｎは金属又は半金属の価数である）を満たす数であり、Ｍは金属元素又は半金属元素である。］で表される化合物が挙げられる。 As the oxide, for example, MO X [in the formula, X is a number satisfying the formula: n / 100 ≦ X ≦ n / 2 (n is a valence of a metal or a semi-metal), and M is a metal element or It is a semi-metallic element. ], Examples thereof include compounds represented by.
　上記窒化物としては、例えばＭＮｙ［式中、Ｙは式：ｎ／１００≦Ｙ≦ｎ／３（ｎは金属又は半金属の価数である）を満たす数であり、Ｍは金属元素又は半金属元素である。］で表される化合物が挙げられる。 As the nitride, for example, MN y [in the formula, Y is a number satisfying the formula: n / 100 ≦ Y ≦ n / 3 (n is a valence of a metal or a semi-metal), and M is a metal element or It is a semi-metallic element. ], Examples thereof include compounds represented by.
　上記窒化酸化物としては、例えばＭＯＸＮｙ［式中、ＸとＹは、ｎ／１００≦Ｘ、ｎ／１００≦Ｙ、かつ、Ｘ＋Ｙ≦ｎ／２（ｎは金属又は半金属の価数である）であり、Ｍは金属元素又は半金属元素である。］で表される化合物が挙げられる。 Examples of the nitride oxide include MO X N y [in the formula, X and Y are n / 100 ≦ X, n / 100 ≦ Y, and X + Y ≦ n / 2 (n is a valence of a metal or a metalloid). ), And M is a metal element or a metalloid element. ], Examples thereof include compounds represented by.
　上記酸化物又は窒化酸化物の酸化数Ｘに関しては、例えばＭＯｘ又はＭＯｘＮｙを含む層の断面を、ＦＥ－ＴＥＭ－ＥＤＸ（例えば、日本電子社製「ＪＥＭ－ＡＲＭ２００Ｆ」）により元素分析し、ＭＯｘ又はＭＯｘＮｙを含む層の断面の面積当たりのＭとＯとの元素比率からＸを算出することにより、酸素原子の価数を算出することができる。 For the oxidation number X of the oxide or oxynitride, for example MO a cross-section of the layer containing the x or MO x N y, FE-TEM -EDX ( e.g., manufactured by JEOL Ltd. "JEM-ARM200F") Elemental analysis Then, the valence of the oxygen atom can be calculated by calculating X from the elemental ratio of M and O per area of the cross section of the layer containing MO x or MO x N y .
　上記窒化物又は窒化酸化物の窒素化数Ｙに関しては、例えばＭＮｙ又はＭＯｘＮｙを含む層の断面を、ＦＥ－ＴＥＭ－ＥＤＸ（例えば、日本電子社製「ＪＥＭ－ＡＲＭ２００Ｆ」）により元素分析し、ＭＮｙ又はＭＯｘＮｙを含む層の断面の面積当たりのＭとＮとの元素比率からＹを算出することにより、窒素原子の価数を算出することができる。 Regarding the nitrogen oxide number Y of the nitride or nitride oxide, for example, the cross section of the layer containing MN y or MO x N y is elementalized by FE-TEM-EDX (for example, "JEM-ARM200F" manufactured by JEOL Ltd.). The valence of nitrogen atoms can be calculated by analyzing and calculating Y from the elemental ratio of M and N per area of the cross section of the layer containing MN y or MO x N y .
　バリア層の素材の具体例としては、ＳｉＯ２、ＳｉＯｘ、Ａｌ２Ｏ３、ＭｇＡｌ２Ｏ４、ＣｕＯ、ＣｕＮ、ＴｉＯ２、ＴｉＮ、ＡＺＯ（アルミニウムドープ酸化亜鉛）等が挙げられる。 Specific examples of the material of the barrier layer include SiO 2 , SiO x , Al 2 O 3 , MgAl 2 O 4 , CuO, CuN, TiO 2 , TiN, AZO (aluminum-doped zinc oxide) and the like.
　バリア層の厚みは、特に制限されない。バリア層の厚みは、例えば１ｎｍ以上２００ｎｍ以下、好ましくは１ｎｍ以上１００ｎｍ以下、より好ましくは１ｎｍ以上２０ｎｍ以下である。 The thickness of the barrier layer is not particularly limited. The thickness of the barrier layer is, for example, 1 nm or more and 200 nm or less, preferably 1 nm or more and 100 nm or less, and more preferably 1 nm or more and 20 nm or less.
　バリア層の層構成は特に制限されない。バリア層は、１種単独のバリア層から構成されるものであってもよいし、２種以上のバリア層が複数組み合わされたものであってもよい。 The layer structure of the barrier layer is not particularly limited. The barrier layer may be composed of one type of barrier layer alone, or may be a combination of two or more types of barrier layers.
　＜２－３．誘電体層＞
　誘電体層は、電波吸収体において目的の波長に対して誘電体として機能し得るものである限り、特に制限されない。誘電体層としては、特に制限されないが、例えば樹脂シート、粘着剤等が挙げられる。 <2-3. Dielectric layer>
The dielectric layer is not particularly limited as long as it can function as a dielectric for a target wavelength in the radio wave absorber. The dielectric layer is not particularly limited, and examples thereof include a resin sheet and an adhesive.
　樹脂シートは、樹脂を素材として含むシート状のものである限り、特に制限されない。樹脂シートは、本発明の効果が著しく損なわれない限りにおいて、樹脂以外の成分が含まれていてもよい。その場合、樹脂シート中の樹脂の合計量は、例えば５０質量％以上、好ましくは７０質量％以上、より好ましくは９０質量％以上、さらに好ましくは９５質量％以上であり、通常１００質量％未満である。 The resin sheet is not particularly limited as long as it is in the form of a sheet containing resin as a material. The resin sheet may contain components other than the resin as long as the effects of the present invention are not significantly impaired. In that case, the total amount of the resin in the resin sheet is, for example, 50% by mass or more, preferably 70% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and usually less than 100% by mass. is there.
　樹脂としては、特に制限されず、例えばエチレン酢酸ビニル共重合体（ＥＶＡ）、塩化ビニル、ウレタン、アクリル、アクリルウレタン、ポリオレフィン、ポリエチレン、ポリプロピレン、シリコーン、ポリエチレンテレフタレート、ポリエステル、ポリスチレン、ポリイミド、ポリカーボネート、ポリアミド、ポリサルフォン、ポリエーテルサルフォン、エポキシ等の合成樹脂や、ポリイソプレンゴム、ポリスチレン・ブタジエンゴム、ポリブタジエンゴム、クロロプレンゴム、アクリロニトリル・ブタジエンゴム、ブチルゴム、アクリルゴム、エチレン・プロピレンゴムおよびシリコーンゴム等の合成ゴム材料を樹脂成分として用いることが好ましい。これらは１種単独でまたは２種以上の組合せで使用することができる。 The resin is not particularly limited, for example, ethylene vinyl acetate copolymer (EVA), vinyl chloride, urethane, acrylic, acrylic urethane, polyolefin, polyethylene, polypropylene, silicone, polyethylene terephthalate, polyester, polystyrene, polyimide, polycarbonate, polyamide. , Polysulfone, polyether sulfone, epoxy and other synthetic resins, polyisoprene rubber, polystyrene / butadiene rubber, polybutadiene rubber, chloroprene rubber, acrylonitrile / butadiene rubber, butyl rubber, acrylic rubber, ethylene / propylene rubber and silicone rubber. It is preferable to use a rubber material as a resin component. These can be used alone or in combination of two or more.
　誘電体層は、発泡体や粘着剤であってもよい。粘着剤としては、特に制限されず、例えばアクリル系粘着剤、ウレタン系粘着剤、ポリオレフィン系粘着剤、ポリエステル系粘着剤、ビニルアルキルエーテル系粘着剤、ポリアミド系粘着剤、ゴム系粘着剤、シリコーン系粘着剤、フッ素系粘着剤等が挙げられる。これらの中でも、耐候性が高いという観点から、アクリル系粘着剤が好ましい。 The dielectric layer may be a foam or an adhesive. The adhesive is not particularly limited, and for example, acrylic adhesive, urethane adhesive, polyolefin adhesive, polyester adhesive, vinyl alkyl ether adhesive, polyamide adhesive, rubber adhesive, silicone adhesive. Examples include adhesives and fluorine-based adhesives. Among these, an acrylic adhesive is preferable from the viewpoint of high weather resistance.
　誘電体層は、粘着性を備えるものであってもよい。このため、粘着性を有しない誘電体を粘着剤層により他の層に積層させる場合、該誘電体と粘着剤層とを合わせたものが「誘電体層」となる。隣接する層と積層し易いという観点から、誘電体層は、好ましくは粘着剤層を含む。 The dielectric layer may have adhesiveness. Therefore, when a dielectric having no adhesiveness is laminated on another layer by the pressure-sensitive adhesive layer, the combination of the dielectric and the pressure-sensitive adhesive layer becomes a "dielectric layer". The dielectric layer preferably includes an adhesive layer from the viewpoint of easy stacking with the adjacent layer.
　誘電体層の比誘電率は、本発明の特性を満たし得るものである限り特に制限されない。誘電体層の比誘電率は、例えば１～２０、好ましくは１～１５、より好ましくは１～１０である。中でも、誘電率の温度変化をより低く抑えることができるという観点から、誘電体層の比誘電率は、特に好ましくは１～５である。 The relative permittivity of the dielectric layer is not particularly limited as long as it can satisfy the characteristics of the present invention. The relative permittivity of the dielectric layer is, for example, 1 to 20, preferably 1 to 15, and more preferably 1 to 10. Above all, the relative permittivity of the dielectric layer is particularly preferably 1 to 5 from the viewpoint that the temperature change of the dielectric constant can be suppressed to a lower level.
　誘電体層の比誘電率は、１ＭＨｚにおける値を、キーサイト社製誘電率測定装置（プレシジョンＬＣＲメーターＥ４９８０ＡＬ）及びキーコム社製測定用電極（ＤＰＴ－２１４１－０１）により測定することができる。 The relative permittivity of the dielectric layer can be measured at 1 MHz with a dielectric constant measuring device (Precision LCR meter E4980AL) manufactured by Keysight and a measuring electrode (DPT-2141-01) manufactured by Keycom.
　誘電体層のガラス転移温度Ｔｇは、本発明の特性を満たし得るものである限り特に制限されない。誘電体層のガラス転移温度Ｔｇは、本発明の特性の観点から、好ましくは－１０℃以上、より好ましくは－８℃以上、さらに好ましくは－６℃以上である。該温度の上限は、特に制限されず、例えば１５０℃、２００℃である。 The glass transition temperature Tg of the dielectric layer is not particularly limited as long as it can satisfy the characteristics of the present invention. From the viewpoint of the characteristics of the present invention, the glass transition temperature Tg of the dielectric layer is preferably −10 ° C. or higher, more preferably −8 ° C. or higher, still more preferably −6 ° C. or higher. The upper limit of the temperature is not particularly limited, and is, for example, 150 ° C. and 200 ° C.
　誘電体層のガラス転移温度Ｔｇは、動的粘弾性測定装置（ＡＲＥＳ－Ｇ２（ＴＡ　Ｉｎｓｔｒｕｍｅｎｔｓ社製）、又はその同等品）を用い、周波数１０Ｈｚ、温度範囲－１００℃～２５０℃にて測定を行い、ガラス転移温度Ｔｇを算出することにより測定することができる。 The glass transition temperature Tg of the dielectric layer is measured using a dynamic viscoelasticity measuring device (ARES-G2 (manufactured by TA Instruments) or its equivalent) at a frequency of 10 Hz and a temperature range of -100 ° C to 250 ° C. It can be measured by calculating the glass transition temperature Tg.
　誘電体層の厚みは、本発明の特性を満たし得るものである限り特に制限されない。誘電体層の厚みは、例えば１００～１０００μｍである。該厚みは、本発明の特性の観点から、好ましくは１５０～９００μｍ、より好ましくは２００～８００μｍである。 The thickness of the dielectric layer is not particularly limited as long as it can satisfy the characteristics of the present invention. The thickness of the dielectric layer is, for example, 100 to 1000 μm. From the viewpoint of the characteristics of the present invention, the thickness is preferably 150 to 900 μm, more preferably 200 to 800 μm.
　誘電体層の厚みは、Ｎｉｋｏｎ　ＤＩＧＩＭＩＣＲＯ　ＳＴＡＮＤＭＳ－１１Ｃ＋Ｎｉｋｏｎ　ＤＩＧＩＭＩＣＲＯ　ＭＦＣ－１０１によって測定することができる。 The thickness of the dielectric layer can be measured by Nikon DIGIMICRO STANDMS-11C + Nikon DIGIMICRO MFC-101.
　誘電体層の層構成は特に制限されない。誘電体層は、１種単独の誘電体層から構成されるものであってもよいし、２種以上の誘電体層が複数組み合わされたものであってもよい。例えば、粘着性を有しない誘電体とその両面に配置された粘着剤層とからなる３層構造の誘電体層、粘着性を有する誘電体からなる１層構造の誘電体層等が挙げられる。 The layer structure of the dielectric layer is not particularly limited. The dielectric layer may be composed of one kind of single dielectric layer, or may be a combination of two or more kinds of dielectric layers. For example, a three-layered dielectric layer composed of a non-adhesive dielectric and adhesive layers arranged on both sides thereof, a one-layered dielectric layer composed of an adhesive dielectric, and the like can be mentioned.
　＜２－４．反射層＞
　反射層は、電波吸収体において電波の反射層として機能し得るものである限り、特に制限されない。反射層としては、特に制限されないが、例えば金属膜が挙げられる。 <2-4. Reflective layer>
The reflective layer is not particularly limited as long as it can function as a radio wave reflecting layer in the radio wave absorber. The reflective layer is not particularly limited, and examples thereof include a metal film.
　金属膜は、金属を素材として含む層である限り、特に制限されない。金属膜は、本発明の効果が著しく損なわれない限りにおいて、金属以外の成分が含まれていてもよい。その場合、金属膜中の金属の合計量は、例えば３０質量％以上、好ましくは５０質量％以上、より好ましくは７５質量％以上、さらに好ましくは８０質量％以上、さらにより好ましくは９０質量％以上、特に好ましくは９５質量％以上、非常に好ましくは９９質量％以上であり、通常１００質量％未満である。 The metal film is not particularly limited as long as it is a layer containing metal as a material. The metal film may contain a component other than the metal as long as the effect of the present invention is not significantly impaired. In that case, the total amount of the metal in the metal film is, for example, 30% by mass or more, preferably 50% by mass or more, more preferably 75% by mass or more, still more preferably 80% by mass or more, still more preferably 90% by mass or more. , Particularly preferably 95% by mass or more, very preferably 99% by mass or more, and usually less than 100% by mass.
　金属としては、特に制限されず、例えばアルミニウム、銅、鉄、銀、金、クロム、ニッケル、モリブデン、ガリウム、亜鉛、スズ、ニオブ、インジウム等が挙げられる。また、金属化合物、例えばＩＴＯ等も、金属膜の素材として使用することができる。これらは１種単独であってもよいし、２種以上の組み合わせであってもよい。 The metal is not particularly limited, and examples thereof include aluminum, copper, iron, silver, gold, chromium, nickel, molybdenum, gallium, zinc, tin, niobium, and indium. Further, a metal compound such as ITO can also be used as a material for the metal film. These may be one kind alone or a combination of two or more kinds.
　反射層の厚みは、特に制限されない。反射層の厚みは、例えば１μｍ以上５００μｍ以下、好ましくは２μｍ以上２００μｍ以下、より好ましくは５μｍ以上１００μｍ以下である。 The thickness of the reflective layer is not particularly limited. The thickness of the reflective layer is, for example, 1 μm or more and 500 μm or less, preferably 2 μm or more and 200 μm or less, and more preferably 5 μm or more and 100 μm or less.
　反射層の層構成は特に制限されない。反射層は、１種単独の反射層から構成されるものであってもよいし、２種以上の反射層が複数組み合わされたものであってもよい。 The layer structure of the reflective layer is not particularly limited. The reflective layer may be composed of one type of single reflective layer, or may be a combination of a plurality of two or more types of reflective layers.
　＜２－５．層構成＞
　本発明のλ／４型電波吸収体が抵抗膜、誘電体層、及び反射層を有する場合、各層は、電波吸収性能を発揮することができる順に配置される。一例として、抵抗膜、誘電体層、及び反射層は、この順に配置される。 <2-5. Layer structure>
When the λ / 4 type radio wave absorber of the present invention has a resistance film, a dielectric layer, and a reflective layer, the layers are arranged in the order in which the radio wave absorption performance can be exhibited. As an example, the resistance film, the dielectric layer, and the reflective layer are arranged in this order.
　さらに、本発明のλ／４型電波吸収体が支持体を有する場合、一例として、支持体、抵抗膜、誘電体層、及び反射層は、この順に配置される。 Further, when the λ / 4 type radio wave absorber of the present invention has a support, the support, the resistance film, the dielectric layer, and the reflective layer are arranged in this order as an example.
　本発明のλ／４型電波吸収体においては、支持体、抵抗膜、誘電体層、及び反射層以外に、他の層を含むものであってもよい。他の層は、支持体、抵抗膜、誘電体層、及び反射層それぞれの層の、どちらか一方の表面上に配置され得る。 The λ / 4 type radio wave absorber of the present invention may include other layers in addition to the support, the resistance film, the dielectric layer, and the reflective layer. The other layer may be placed on the surface of either the support, the resistor film, the dielectric layer, and the reflective layer, respectively.
　＜３．製造方法＞
　本発明のλ／４型電波吸収体は、その構成に応じて、様々な方法、例えば公知の製造方法に従って又は準じて得ることができる。例えば、支持体上に抵抗膜、誘電体層、及び反射層を順に積層させる工程を含む方法により、得ることができる。 <3. Manufacturing method>
The λ / 4 type radio absorber of the present invention can be obtained according to or according to various methods, for example, a known manufacturing method, depending on its configuration. For example, it can be obtained by a method including a step of sequentially laminating a resistance film, a dielectric layer, and a reflective layer on a support.
　積層方法は特に制限されない。 The stacking method is not particularly limited.
　抵抗膜は、例えば、スパッタリング法、真空蒸着法、イオンプレーティング法、化学蒸着法、パルスレーザーデポジション法等により行うことができる。これらの中でも、膜厚制御性の観点から、スパッタリング法が好ましい。スパッタリング法としては、特に限定されないが、例えば、直流マグネトロンスパッタ、高周波マグネトロンスパッタ及びイオンビームスパッタ等が挙げられる。また、スパッタ装置は、バッチ方式であってもロール・ツー・ロール方式であってもよい。 The resistance film can be formed by, for example, a sputtering method, a vacuum vapor deposition method, an ion plating method, a chemical vapor deposition method, a pulse laser deposition method, or the like. Among these, the sputtering method is preferable from the viewpoint of film thickness controllability. The sputtering method is not particularly limited, and examples thereof include DC magnetron sputtering, high frequency magnetron sputtering, and ion beam sputtering. Further, the sputtering apparatus may be a batch system or a roll-to-roll system.
　誘電体層や反射層は、例えば誘電体層が有する粘着性を利用して、積層することができる。 The dielectric layer and the reflective layer can be laminated by utilizing, for example, the adhesiveness of the dielectric layer.
　＜４．λ／４型電波吸収体用部材＞
　本発明は、その一態様において、抵抗膜及び誘電体層を含み、厚さ３０μｍの銅からなる反射層を誘電体層の他方の面に積層した際の、６０～１３０℃における７９ＧＨｚでの電波吸収量の最小値が１０ｄＢ以上である、λ／４型電波吸収体用部材、に関する。なお厚さ３０μｍの銅からなる反射層は、誘電体層と接する表面における表面粗さ（Ｒａ）が０．３ｎｍである銅板又は銅箔テープを用いる。
λ／４型電波吸収体用部材は、反射層として機能し得る被着体に接するように配置することによりλ／４型電波吸収体を形成するための部材である。抵抗膜、誘電体層、本発明の特性、その他の構成については、本発明のλ／４型電波吸収体に関する説明と同様である。 <4. λ / 4 type radio wave absorber member>
In one aspect of the present invention, there is a radio wave at 79 GHz at 60 to 130 ° C. when a reflective layer made of copper having a thickness of 30 μm including a resistance film and a dielectric layer is laminated on the other surface of the dielectric layer. The present invention relates to a λ / 4 type radio wave absorber member having a minimum absorption amount of 10 dB or more. As the reflective layer made of copper having a thickness of 30 μm, a copper plate or copper foil tape having a surface roughness (Ra) of 0.3 nm on the surface in contact with the dielectric layer is used.
The λ / 4 type radio wave absorber member is a member for forming a λ / 4 type radio wave absorber by arranging it in contact with an adherend that can function as a reflective layer. The resistance film, the dielectric layer, the characteristics of the present invention, and other configurations are the same as those described for the λ / 4 type radio wave absorber of the present invention.
　＜５．用途＞
　本発明のλ／４型電波吸収体は、不要な電磁波を吸収する性能を有するため、例えば光トランシーバや、次世代移動通信システム（５Ｇ）、近距離無線転送技術等における電波対策部材として好適に利用できる。また、その他の用途として自動車、道路、人の相互間で情報通信を行う高度道路交通システム（ＩＴＳ）や自動車衝突防止システムに用いるミリ波レーダーにおいても、電波干渉抑制やノイズ低減の目的で用いることができる。 <5. Use>
Since the λ / 4 type radio wave absorber of the present invention has a performance of absorbing unnecessary electromagnetic waves, it is suitable as a radio wave countermeasure member in, for example, an optical transceiver, a next-generation mobile communication system (5G), a short-range wireless transfer technology, and the like. Available. In addition, it should also be used for the purpose of suppressing radio wave interference and reducing noise in intelligent transportation systems (ITS) that communicate information between automobiles, roads, and people, and millimeter-wave radars used in automobile collision prevention systems. Can be done.
　本発明は、その一態様において、本発明のλ／４型電波吸収体を含む、ミリ波レーダー、に関する。 The present invention relates to a millimeter wave radar including the λ / 4 type radio absorber of the present invention in one aspect thereof.
　本発明のλ／４型電波吸収体が対象とする電波の周波数は、好ましくは１０～１５０ＧＨｚ、より好ましくは５０～１００ＧＨｚ、さらに好ましくは７０～９０ＧＨｚである。 The frequency of the radio wave targeted by the λ / 4 type radio wave absorber of the present invention is preferably 10 to 150 GHz, more preferably 50 to 100 GHz, and even more preferably 70 to 90 GHz.
　以下に、実施例に基づいて本発明を詳細に説明するが、本発明はこれらの実施例によって限定されるものではない。 The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.
　（１）誘電体層材料の調製
　（参考例１）
　２－エチルヘキシルアクリレート８５重量部、ブチルアクリレート１５重量部、アクリル酸１０重量部、２，２－ジメトキシ－２－フェニルアセトフェノン０．１５重量部、ヘキサンジオールジアクリレート０．１５重量部を均一に混合して重合性組成物を作成した。この重合性組成物に窒素をパージして溶存酸素を除去した。ついで、離型処理した５０μｍ厚のＰＥＴフィルムの離型処理面上に塗工し、さらに離型処理した５０μｍ厚のＰＥＴフィルムの離型処理面が上記塗工により形成された粘着剤層に面するように、かつ粘着剤層の厚みが０．５ｍｍとなるように離型処理したＰＥＴフィルムに重ね合わせて、被覆側のＰＥＴフィルムにおける紫外線照射強度が５ｍＷ／ｃｍ２となるようにケミカルランプのランプ強度を調整し、１５分間紫外線を照射し、粘着剤層の厚さが０．５ｍｍの粘着テープを得た。 (1) Preparation of dielectric layer material (Reference Example 1)
85 parts by weight of 2-ethylhexyl acrylate, 15 parts by weight of butyl acrylate, 10 parts by weight of acrylic acid, 0.15 parts by weight of 2,2-dimethoxy-2-phenylacetophenone, and 0.15 parts by weight of hexanediol diacrylate are uniformly mixed. To prepare a polymerizable composition. Nitrogen was purged into this polymerizable composition to remove dissolved oxygen. Then, the release-treated 50 μm-thick PET film was coated on the release-treated surface, and the release-treated 50 μm-thick PET film was further coated on the release-treated surface of the 50 μm-thick PET film formed by the above coating. The chemical lamp is superposed on the PET film that has been mold-released so that the thickness of the adhesive layer is 0.5 mm, and the UV irradiation intensity of the PET film on the coating side is 5 mW / cm 2 . The lamp intensity was adjusted and the film was irradiated with ultraviolet rays for 15 minutes to obtain an adhesive tape having an adhesive layer thickness of 0.5 mm.
　（参考例２）
　２－エチルヘキシルアクリレート８５重量部、ブチルアクリレール１５重量部、アクリル酸８重量部、２，２－ジメトキシ－２－フェニルアセトフェノン０．１５重量部、ヘキサンジオールジアクリレート０．１５重量部を均一に混合して重合性組成物を作成した。この重合性組成物に窒素をパージして溶存酸素を除去した。ついで、離型処理した５０μｍ厚のＰＥＴフィルムの離型処理面上に塗工し、さらに離型処理した５０μｍ厚のＰＥＴフィルムの離型処理面が上記塗工により形成された粘着剤層に面するように、かつ粘着剤層の厚みが０．５ｍｍとなるように離型処理したＰＥＴフィルムに重ね合わせて、被覆側のＰＥＴフィルムにおける紫外線照射強度が５ｍＷ／ｃｍ２となるようにケミカルランプのランプ強度を調整し、１５分間紫外線を照射し、粘着剤層の厚さが０．５ｍｍの粘着テープを得た。 (Reference example 2)
85 parts by weight of 2-ethylhexyl acrylate, 15 parts by weight of butylacrylyl, 8 parts by weight of acrylic acid, 0.15 parts by weight of 2,2-dimethoxy-2-phenylacetophenone, 0.15 parts by weight of hexanediol diacrylate are uniformly mixed. To prepare a polymerizable composition. Nitrogen was purged into this polymerizable composition to remove dissolved oxygen. Then, the release-treated 50 μm-thick PET film was coated on the release-treated surface, and the release-treated 50 μm-thick PET film was further coated on the release-treated surface of the 50 μm-thick PET film formed by the above coating. The chemical lamp is superposed on the PET film that has been mold-released so that the thickness of the adhesive layer is 0.5 mm, and the UV irradiation intensity of the PET film on the coating side is 5 mW / cm 2 . The lamp intensity was adjusted and the film was irradiated with ultraviolet rays for 15 minutes to obtain an adhesive tape having an adhesive layer thickness of 0.5 mm.
　（参考例３）
　２－エチルヘキシルアクリレート８５重量部、ブチルアクリレール１５重量部、アクリル酸８重量部、２，２－ジメトキシ－２－フェニルアセトフェノン０．１５重量部、ヘキサンジオールジアクリレート０．１５重量部、堺化学工業社製チタン酸バリウム（ＢＴ－０１）５０重量部を均一に混合して重合性組成物を作成した。この重合性組成物に窒素をパージして溶存酸素を除去した。ついで、離型処理した５０μｍ厚のＰＥＴフィルムの離型処理面上に塗工し、さらに離型処理した５０μｍ厚のＰＥＴフィルムの離型処理面が上記塗工により形成された粘着剤層に面するように、かつ粘着剤層の厚みが０．５ｍｍとなるように離型処理したＰＥＴフィルムに重ね合わせて、被覆側のＰＥＴフィルムにおける紫外線照射強度が５ｍＷ／ｃｍ２となるようにケミカルランプのランプ強度を調整し、１５分間紫外線を照射し、粘着剤層の厚さが０．４ｍｍの粘着テープを得た。 (Reference example 3)
85 parts by weight of 2-ethylhexyl acrylate, 15 parts by weight of butylacrylyl, 8 parts by weight of acrylic acid, 0.15 parts by weight of 2,2-dimethoxy-2-phenylacetophenone, 0.15 parts by weight of hexanediol diacrylate, Sakai Chemical Industry 50 parts by weight of barium titanate (BT-01) manufactured by the same company was uniformly mixed to prepare a polymerizable composition. Nitrogen was purged into this polymerizable composition to remove dissolved oxygen. Then, the release-treated 50 μm-thick PET film was coated on the release-treated surface, and the release-treated 50 μm-thick PET film was further coated on the release-treated surface of the 50 μm-thick PET film formed by the above coating. The chemical lamp is superposed on the PET film that has been mold-released so that the thickness of the adhesive layer is 0.5 mm, and the UV irradiation intensity of the PET film on the coating side is 5 mW / cm 2 . The lamp intensity was adjusted and irradiated with ultraviolet rays for 15 minutes to obtain an adhesive tape having an adhesive layer thickness of 0.4 mm.
　（参考例４）
　ポリエチレン加熱発泡シート状高発泡体（積水化学社製、ソフトロンＳ）を使用した。 (Reference example 4)
A polyethylene heated foam sheet-like high foam (manufactured by Sekisui Chemical Co., Ltd., Softlon S) was used.
　（参考例５）
　２－エチルヘキシルアクリレート８５重量部、ブチルアクリレール１５重量部、アクリル酸３重量部、２，２－ジメトキシ－２－フェニルアセトフェノン０．１５重量部、ヘキサンジオールジアクリレート０．１５重量部、堺化学工業社製チタン酸バリウム（ＢＴ－０１）６０重量部を均一に混合して重合性組成物を作成した。この重合性組成物に窒素をパージして溶存酸素を除去した。ついで、離型処理した５０μｍ厚のＰＥＴフィルムの離型処理面上に塗工し、さらに離型処理した５０μｍ厚のＰＥＴフィルムの離型処理面が上記塗工により形成された粘着剤層に面するように、かつ粘着剤層の厚みが０．５ｍｍとなるように離型処理したＰＥＴフィルムに重ね合わせて、被覆側のＰＥＴフィルムにおける紫外線照射強度が５ｍＷ／ｃｍ２となるようにケミカルランプのランプ強度を調整し、１５分間紫外線を照射し、粘着剤層の厚さが１．１ｍｍの粘着テープを得た。 (Reference example 5)
85 parts by weight of 2-ethylhexyl acrylate, 15 parts by weight of butylacrylyl, 3 parts by weight of acrylic acid, 0.15 parts by weight of 2,2-dimethoxy-2-phenylacetophenone, 0.15 parts by weight of hexanediol diacrylate, Sakai Chemical Industry 60 parts by weight of barium titanate (BT-01) manufactured by the same company was uniformly mixed to prepare a polymerizable composition. Nitrogen was purged into this polymerizable composition to remove dissolved oxygen. Then, the release-treated 50 μm-thick PET film was coated on the release-treated surface, and the release-treated 50 μm-thick PET film was further coated on the release-treated surface of the 50 μm-thick PET film formed by the above coating. The chemical lamp is superposed on the PET film that has been mold-released so that the thickness of the adhesive layer is 0.5 mm, and the UV irradiation intensity of the PET film on the coating side is 5 mW / cm 2 . The lamp intensity was adjusted and irradiated with ultraviolet rays for 15 minutes to obtain an adhesive tape having an adhesive layer thickness of 1.1 mm.
　（参考例６）
　２－エチルヘキシルアクリレート８５重量部、ブチルアクリレール１５重量部、アクリル酸３重量部、２，２－ジメトキシ－２－フェニルアセトフェノン０．１５重量部、ヘキサンジオールジアクリレート０．１５重量部、堺化学工業社製チタン酸バリウム（ＢＴ－０１）７０重量部を均一に混合して重合性組成物を作成した。この重合性組成物に窒素をパージして溶存酸素を除去した。ついで、離型処理した５０μｍ厚のＰＥＴフィルムの離型処理面上に塗工し、さらに離型処理した５０μｍ厚のＰＥＴフィルムの離型処理面が上記塗工により形成された粘着剤層に面するように、かつ粘着剤層の厚みが０．５ｍｍとなるように離型処理したＰＥＴフィルムに重ね合わせて、被覆側のＰＥＴフィルムにおける紫外線照射強度が５ｍＷ／ｃｍ２となるようにケミカルランプのランプ強度を調整し、１５分間紫外線を照射し、粘着剤層の厚さが１．８ｍｍの粘着テープを得た。 (Reference example 6)
85 parts by weight of 2-ethylhexyl acrylate, 15 parts by weight of butylacrylyl, 3 parts by weight of acrylic acid, 0.15 parts by weight of 2,2-dimethoxy-2-phenylacetophenone, 0.15 parts by weight of hexanediol diacrylate, Sakai Chemical Industry 70 parts by weight of barium titanate (BT-01) manufactured by the same company was uniformly mixed to prepare a polymerizable composition. Nitrogen was purged into this polymerizable composition to remove dissolved oxygen. Then, the release-treated 50 μm-thick PET film was coated on the release-treated surface, and the release-treated 50 μm-thick PET film was further coated on the release-treated surface of the 50 μm-thick PET film formed by the above coating. The chemical lamp is superposed on the PET film that has been mold-released so that the thickness of the adhesive layer is 0.5 mm, and the UV irradiation intensity of the PET film on the coating side is 5 mW / cm 2 . The lamp intensity was adjusted and the film was irradiated with ultraviolet rays for 15 minutes to obtain an adhesive tape having a thickness of the adhesive layer of 1.8 mm.
　（参考例７）
　２－エチルヘキシルアクリレート８５重量部、ブチルアクリレール１５重量部、アクリル酸４重量部、２，２－ジメトキシ－２－フェニルアセトフェノン０．１５重量部、ヘキサンジオールジアクリレート０．１５重量部、堺化学工業社製チタン酸バリウム（ＢＴ－０１）８０重量部を均一に混合して重合性組成物を作成した。この重合性組成物に窒素をパージして溶存酸素を除去した。ついで、離型処理した５０μｍ厚のＰＥＴフィルムの離型処理面上に塗工し、さらに離型処理した５０μｍ厚のＰＥＴフィルムの離型処理面が上記塗工により形成された粘着剤層に面するように、かつ粘着剤層の厚みが０．５ｍｍとなるように離型処理したＰＥＴフィルムに重ね合わせて、被覆側のＰＥＴフィルムにおける紫外線照射強度が５ｍＷ／ｃｍ２となるようにケミカルランプのランプ強度を調整し、１５分間紫外線を照射し、粘着剤層の厚さが１．７ｍｍの粘着テープを得た。 (Reference example 7)
85 parts by weight of 2-ethylhexyl acrylate, 15 parts by weight of butylacrylyl, 4 parts by weight of acrylic acid, 0.15 parts by weight of 2,2-dimethoxy-2-phenylacetophenone, 0.15 parts by weight of hexanediol diacrylate, Sakai Chemical Industry 80 parts by weight of barium titanate (BT-01) manufactured by the same company was uniformly mixed to prepare a polymerizable composition. Nitrogen was purged into this polymerizable composition to remove dissolved oxygen. Then, the release-treated 50 μm-thick PET film was coated on the release-treated surface, and the release-treated 50 μm-thick PET film was further coated on the release-treated surface of the 50 μm-thick PET film formed by the above coating. The chemical lamp is superposed on the PET film that has been mold-released so that the thickness of the adhesive layer is 0.5 mm, and the UV irradiation intensity of the PET film on the coating side is 5 mW / cm 2 . The lamp intensity was adjusted and the film was irradiated with ultraviolet rays for 15 minutes to obtain an adhesive tape having an adhesive layer thickness of 1.7 mm.
　（参考例８）
　２－エチルヘキシルアクリレート８５重量部、ブチルアクリレール１５重量部、アクリル酸４重量部、２，２－ジメトキシ－２－フェニルアセトフェノン０．１５重量部、ヘキサンジオールジアクリレート０．１５重量部、堺化学工業社製チタン酸バリウム（ＢＴ－０１）６０重量部を均一に混合して重合性組成物を作成した。この重合性組成物に窒素をパージして溶存酸素を除去した。ついで、離型処理した５０μｍ厚のＰＥＴフィルムの離型処理面上に塗工し、さらに離型処理した５０μｍ厚のＰＥＴフィルムの離型処理面が上記塗工により形成された粘着剤層に面するように、かつ粘着剤層の厚みが０．５ｍｍとなるように離型処理したＰＥＴフィルムに重ね合わせて、被覆側のＰＥＴフィルムにおける紫外線照射強度が５ｍＷ／ｃｍ２となるようにケミカルランプのランプ強度を調整し、１５分間紫外線を照射し、粘着剤層の厚さが１．１ｍｍの粘着テープを得た。 (Reference example 8)
85 parts by weight of 2-ethylhexyl acrylate, 15 parts by weight of butylacrylyl, 4 parts by weight of acrylic acid, 0.15 parts by weight of 2,2-dimethoxy-2-phenylacetophenone, 0.15 parts by weight of hexanediol diacrylate, Sakai Chemical Industry 60 parts by weight of barium titanate (BT-01) manufactured by the same company was uniformly mixed to prepare a polymerizable composition. Nitrogen was purged into this polymerizable composition to remove dissolved oxygen. Then, the release-treated 50 μm-thick PET film was coated on the release-treated surface, and the release-treated 50 μm-thick PET film was further coated on the release-treated surface of the 50 μm-thick PET film formed by the above coating. The chemical lamp is superposed on the PET film that has been mold-released so that the thickness of the adhesive layer is 0.5 mm, and the UV irradiation intensity of the PET film on the coating side is 5 mW / cm 2 . The lamp intensity was adjusted and the film was irradiated with ultraviolet rays for 15 minutes to obtain an adhesive tape having an adhesive layer thickness of 1.1 mm.
　（２）λ／４型電波吸収体の製造
　（実施例１）
　支持体として、厚み１２５μｍのポリエステルフィルム（比誘電率３．３、ガラス転移温度Ｔｇ８０℃、１００℃での加熱収縮率０．２５％）（三菱ケミカル社製、ダイアホイル）を用意した。上記ＰＥＴフィルム上に、ＤＣスパッタリングにより、厚み１１．１ｎｍ且つシート抵抗値３４１Ω／□の抵抗膜を形成した。スパッタリングはハステロイＣ－２７６をターゲットに用い、出力０．４ｋＷ、Ａｒガス流量１００ｓｃｃｍで導入して圧力０．１２Ｐａとなるように調整して行った。次いで、形成した抵抗膜上に厚み０．５ｍｍのアクリル両面粘着テープ（参考例１：比誘電率３．１、ガラス転移温度Ｔｇ０℃）からなる誘電体を積層し、更に誘電体上に厚さ３０μｍの銅からなる反射層（銅箔、Ｒａ＝０．３ｎｍ）を積層して、λ／４型電波吸収体を得た。 (2) Manufacture of λ / 4 type radio wave absorber (Example 1)
As a support, a polyester film having a thickness of 125 μm (relative permittivity 3.3, glass transition temperature Tg 80 ° C., heat shrinkage rate 0.25% at 100 ° C.) (diafoil manufactured by Mitsubishi Chemical Corporation) was prepared. A resistance film having a thickness of 11.1 nm and a sheet resistance value of 341 Ω / □ was formed on the PET film by DC sputtering. Sputtering was carried out using Hastelloy C-276 as a target, introduced at an output of 0.4 kW and an Ar gas flow rate of 100 sccm, and adjusted to a pressure of 0.12 Pa. Next, a dielectric material made of an acrylic double-sided adhesive tape having a thickness of 0.5 mm (reference example 1: relative permittivity 3.1, glass transition temperature Tg 0 ° C.) was laminated on the formed resistance film, and further thickened on the dielectric material. A reflective layer (copper foil, Ra = 0.3 nm) made of 30 μm copper was laminated to obtain a λ / 4 type radio wave absorber.
　（実施例２）
　抵抗膜を厚み１１．０ｎｍ且つシート抵抗値３４５Ω／□とし、且つ誘電体として参考例２のアクリル両面粘着テープを使用する以外は、実施例１と同様にしてλ／４型電波吸収体を得た。 (Example 2)
A λ / 4 type radio wave absorber was obtained in the same manner as in Example 1 except that the resistance film had a thickness of 11.0 nm, the sheet resistance value was 345 Ω / □, and the acrylic double-sided adhesive tape of Reference Example 2 was used as the dielectric. It was.
　（実施例３）
　抵抗膜を厚み１０．８ｎｍ且つシート抵抗値３５３Ω／□とし、且つ誘電体として参考例３のアクリル両面粘着テープを使用する以外は、実施例１と同様にしてλ／４型電波吸収体を得た。 (Example 3)
A λ / 4 type radio wave absorber was obtained in the same manner as in Example 1 except that the resistance film had a thickness of 10.8 nm, the sheet resistance value was 353 Ω / □, and the acrylic double-sided adhesive tape of Reference Example 3 was used as the dielectric. It was.
　（実施例４）
　支持体として、厚み２００μｍのポリプロピレンフィルム（比誘電率２．９、ガラス転移温度Ｔｇ０℃、１００℃での加熱収縮率０．４％）（アクリサンデー社製、ＰＰクラフトフィルム）を使用し、抵抗膜を厚み１１．０ｎｍ且つシート抵抗値３４５Ω／□とし、且つ誘電体として参考例４のポリエチレン加熱発泡シート状高発泡体（厚み０．６ｍｍ）を、その両側に粘着テープ（アクリル両面粘着テープ、厚み３０μｍ、比誘電率３．０）を介して積層する以外は、実施例１と同様にしてλ／４型電波吸収体を得た。 (Example 4)
As a support, a polypropylene film having a thickness of 200 μm (relative permittivity 2.9, glass transition temperature Tg 0 ° C., heat shrinkage rate 0.4% at 100 ° C.) (PP craft film manufactured by Acrysandy Co., Ltd.) is used, and a resistance film is used. The thickness is 11.0 nm, the sheet resistance value is 345 Ω / □, and the polyethylene-heated foam sheet-like high foam (thickness 0.6 mm) of Reference Example 4 is used as a dielectric, and adhesive tapes (acrylic double-sided adhesive tape, thickness) are used on both sides thereof. A λ / 4 type radio absorber was obtained in the same manner as in Example 1 except that the film was laminated via 30 μm and a relative permittivity of 3.0).
　（実施例５）
　抵抗膜を厚み１０．９ｎｍ且つシート抵抗値３５２Ω／□とし、且つ誘電体として参考例５のアクリル両面粘着テープを使用する以外は、実施例１と同様にしてλ／４型電波吸収体を得た。 (Example 5)
A λ / 4 type radio wave absorber was obtained in the same manner as in Example 1 except that the resistance film had a thickness of 10.9 nm, the sheet resistance value was 352 Ω / □, and the acrylic double-sided adhesive tape of Reference Example 5 was used as the dielectric. It was.
（実施例６）
支持体として、厚み１２５μｍのポリ乳酸フィルム（比誘電率２．６、ガラス転移温度Ｔｇ４０℃、１００℃での加熱収縮率０．４％）（三菱ケミカル社製）を使用し、抵抗膜を厚み１２ｎｍ且つシート抵抗値３５１Ω／□とする以外は、実施例１と同様にしてλ／４型電波吸収体を得た。 (Example 6)
As a support, a polylactic acid film having a thickness of 125 μm (relative permittivity 2.6, glass transition temperature Tg 40 ° C., heat shrinkage rate 0.4% at 100 ° C.) (manufactured by Mitsubishi Chemical Corporation) is used, and the resistance film is thickened. A λ / 4 type radio wave absorber was obtained in the same manner as in Example 1 except that the thickness was 12 nm and the sheet resistance value was 351 Ω / □.
　（比較例１）
　抵抗膜を厚み１０．５ｎｍ且つシート抵抗値３６０Ω／□とし、且つ誘電体として参考例６のアクリル両面粘着テープを使用する以外は、実施例１と同様にしてλ／４型電波吸収体を得た。 (Comparative Example 1)
A λ / 4 type radio wave absorber was obtained in the same manner as in Example 1 except that the resistance film had a thickness of 10.5 nm, the sheet resistance value was 360 Ω / □, and the acrylic double-sided adhesive tape of Reference Example 6 was used as the dielectric. It was.
　（比較例２）
　抵抗膜を厚み１０．７ｎｍ且つシート抵抗値３５３Ω／□とし、且つ誘電体として参考例７のアクリル両面粘着テープを使用する以外は、実施例１と同様にしてλ／４型電波吸収体を得た。 (Comparative Example 2)
A λ / 4 type radio wave absorber was obtained in the same manner as in Example 1 except that the resistance film had a thickness of 10.7 nm, the sheet resistance value was 353 Ω / □, and the acrylic double-sided adhesive tape of Reference Example 7 was used as the dielectric. It was.
　（比較例３）
　支持体として、厚み１２５μｍのポリウレタンフィルム（比誘電率５．６、ガラス転移温度Ｔｇ－２０℃、１００℃での加熱収縮率０．９％）（日本ユニポリマー社製、ポリウレタンフィルム）を使用し、抵抗膜を厚み１０．８ｎｍ且つシート抵抗値３５０Ω／□とし、且つ誘電体として参考例８のアクリル両面粘着テープを使用する以外は、実施例１と同様にしてλ／４型電波吸収体を得た。 (Comparative Example 3)
A 125 μm-thick polyurethane film (relative permittivity 5.6, glass transition temperature Tg-20 ° C, heat shrinkage 0.9% at 100 ° C) (polyurethane film manufactured by Nippon Unipolymer Co., Ltd.) was used as the support. A λ / 4 type radio wave absorber is used in the same manner as in Example 1 except that the resistance film has a thickness of 10.8 nm, the sheet resistance value is 350 Ω / □, and the acrylic double-sided adhesive tape of Reference Example 8 is used as the dielectric. Obtained.
　（３）測定、評価
　（３－１）６０～１３０℃における７９ＧＨｚでの電波吸収量の測定
　ネットワークアナライザー　ＭＳ４６４７Ｂ（アンリツ社製）、フリースペース材料測定置　ＢＤ１－２６．Ａ（キーコム社製）を用いて電波吸収測定装置を構成した。この電波吸収測定装置を用いて、得られたλ／４型電波電磁波吸収体の７９ＧＨｚでの電波吸収量をＪＩＳ　Ｒ１６７９に基づいて測定した。なお、λ／４型電波吸収体は、電波入射方向が垂直入射かつ基材側からの入射となるようにセットした。電波吸収量測定時は、電波が入射する面とは反対の面からポリイミドヒーター等で加熱を行い電波吸収体の表面温度の調節を行った。 (3) Measurement and evaluation (3-1) Measurement of radio wave absorption at 79 GHz at 60 to 130 ° C. Network analyzer MS4647B (manufactured by Anritsu), free space material measurement device BD1-26. A radio wave absorption measuring device was constructed using A (manufactured by Keycom). Using this radio wave absorption measuring device, the radio wave absorption amount of the obtained λ / 4 type radio wave electromagnetic wave absorber at 79 GHz was measured based on JIS R1679. The λ / 4 type radio wave absorber was set so that the radio wave incident direction was vertical incident and incident from the base material side. When measuring the amount of radio wave absorption, the surface temperature of the radio wave absorber was adjusted by heating with a polyimide heater or the like from the surface opposite to the surface on which the radio wave was incident.
　（３－２）低温～高温における電波吸収量の評価
　上記（３－１）と同様にして－４０～１３０℃における７９ＧＨｚでの電波吸収量を測定した。なお、室温より低温における電波吸収量測定時は、電波が入射する面とは反対の面から電子冷却素子（パスカル社製）で冷却を行い電波吸収体の表面温度の調節を行った。
以下の基準に基づいて評価した。
○：測定温度範囲における７９ＧＨｚでの電波吸収量の最小値が１０ｄＢ以上
×：測定温度範囲における７９ＧＨｚでの電波吸収量の最小値が１０ｄＢ未満。 (3-2) Evaluation of radio wave absorption amount at low temperature to high temperature The radio wave absorption amount at 79 GHz at -40 to 130 ° C. was measured in the same manner as in (3-1) above. When measuring the amount of radio wave absorption at a temperature lower than room temperature, the surface temperature of the radio wave absorber was adjusted by cooling with an electronic cooling element (manufactured by Pascal) from the surface opposite to the surface on which the radio wave is incident.
The evaluation was based on the following criteria.
◯: The minimum value of the radio wave absorption amount at 79 GHz in the measurement temperature range is 10 dB or more ×: The minimum value of the radio wave absorption amount at 79 GHz in the measurement temperature range is less than 10 dB.
　（４）結果
　結果を表１に示す。 (4) Results The results are shown in Table 1.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　１　　支持体
　２　　抵抗膜
　３　　誘電体層
　４　　反射層
　５　　粘着剤層
　６　　筐体 1 Support 2 Resistive film 3 Dielectric layer 4 Reflective layer 5 Adhesive layer 6 Housing

Claims (8)

  1. ６０～１３０℃における７９ＧＨｚでの電波吸収量の最小値が１０ｄＢ以上である、λ／４型電波吸収体。 A λ / 4 type radio wave absorber having a minimum value of radio wave absorption at 79 GHz at 60 to 130 ° C. of 10 dB or more.
  2. 誘電体層を含み、前記誘電体層のガラス転移温度Ｔｇが－１０℃以上である、請求項１に記載のλ／４型電波吸収体。 The λ / 4 type radio wave absorber according to claim 1, which includes a dielectric layer and has a glass transition temperature Tg of the dielectric layer of −10 ° C. or higher.
  3. 誘電体層を含み、前記誘電体層の比誘電率が１～５である、請求項１又は２に記載のλ／４型電波吸収体。 The λ / 4 type radio wave absorber according to claim 1 or 2, which includes a dielectric layer and has a relative permittivity of 1 to 5 of the dielectric layer.
  4. 支持体を含み、前記支持体のガラス転移温度Ｔｇが４０℃以上である、請求項１～３のいずれかに記載のλ／４型電波吸収体。 The λ / 4 type radio wave absorber according to any one of claims 1 to 3, which includes a support and has a glass transition temperature Tg of the support of 40 ° C. or higher.
  5. 前記支持体の１５０℃、６０分加熱後のＭＤ方向及びＴＤ方向ともに加熱収縮率の絶対値が０．５％以下である、請求項４に記載のλ／４型電波吸収体。 The λ / 4 type radio wave absorber according to claim 4, wherein the absolute value of the heat shrinkage rate is 0.5% or less in both the MD direction and the TD direction after heating the support at 150 ° C. for 60 minutes.
  6. 支持体を含み、前記支持体の比誘電率が１～５である、請求項１～５のいずれかに記載のλ／４型電波吸収体。 The λ / 4 type radio wave absorber according to any one of claims 1 to 5, which includes a support and has a relative permittivity of 1 to 5 of the support.
  7. 請求項１～６のいずれかに記載のλ／４型電波吸収体を含む、ミリ波レーダー。 A millimeter-wave radar comprising the λ / 4 type radio wave absorber according to any one of claims 1 to 6.
  8. 抵抗膜及び誘電体層を含み、厚さ３０μｍの銅からなる反射層を誘電体層の他方の面に積層した際の、６０～１３０℃における７９ＧＨｚでの電波吸収量の最小値が１０ｄＢ以上である、λ／４型電波吸収体用部材。 When a reflective layer made of copper with a thickness of 30 μm including a resistance film and a dielectric layer is laminated on the other surface of the dielectric layer, the minimum value of radio wave absorption at 79 GHz at 60 to 130 ° C. is 10 dB or more. There is a member for λ / 4 type radio wave absorber.
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2018056562A (en) * 2016-09-23 2018-04-05 積水化学工業株式会社 RESISTANCE FILM FOR λ/4 TYPE RADIO WAVE ABSORBER AND λ/4 TYPE RADIO WAVE ABSORBER
JP2018098367A (en) * 2016-12-14 2018-06-21 日東電工株式会社 Electromagnetic wave absorber
JP2018147999A (en) * 2017-03-03 2018-09-20 日東電工株式会社 Electromagnetic wave absorber and electromagnetic wave absorber-attached molded product

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2018056562A (en) * 2016-09-23 2018-04-05 積水化学工業株式会社 RESISTANCE FILM FOR λ/4 TYPE RADIO WAVE ABSORBER AND λ/4 TYPE RADIO WAVE ABSORBER
JP2018098367A (en) * 2016-12-14 2018-06-21 日東電工株式会社 Electromagnetic wave absorber
JP2018147999A (en) * 2017-03-03 2018-09-20 日東電工株式会社 Electromagnetic wave absorber and electromagnetic wave absorber-attached molded product

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