WO2023090326A1 - Feuille absorbant les ondes électromagnétiques - Google Patents

Feuille absorbant les ondes électromagnétiques Download PDF

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WO2023090326A1
WO2023090326A1 PCT/JP2022/042433 JP2022042433W WO2023090326A1 WO 2023090326 A1 WO2023090326 A1 WO 2023090326A1 JP 2022042433 W JP2022042433 W JP 2022042433W WO 2023090326 A1 WO2023090326 A1 WO 2023090326A1
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conductive layer
electromagnetic wave
wave absorbing
heat conductive
thermally conductive
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PCT/JP2022/042433
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English (en)
Japanese (ja)
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知範 関
雅道 石久保
健史 小山
勝紀 武藤
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積水ポリマテック株式会社
積水化学工業株式会社
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Publication of WO2023090326A1 publication Critical patent/WO2023090326A1/fr

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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
    • 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
    • B32B7/027—Thermal 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 an electromagnetic wave absorbing sheet.
  • Patent Document 1 an insulating silicone rubber layer containing a thermally conductive filler is laminated on at least one side of a conductive silicone rubber layer filled with short fibrous pitch-based carbon fibers, and the inside or An invention relating to a thermally conductive electromagnetic shielding sheet having a sheet of resin fibers coated with metal on its surface is disclosed. It is described that the thermally conductive electromagnetic wave shielding sheet described in Patent Document 1 has both thermal conductivity (heat dissipation) and electromagnetic wave shielding properties.
  • sheets with electromagnetic wave shielding properties can suppress noise transmission by reflecting noise (electromagnetic waves). was likely to cause Therefore, there is a demand for materials that are excellent in electromagnetic wave absorption.
  • a conductive nonwoven fabric having a metal layer on at least one side has a sheet resistance of 250 to 600 ⁇ / ⁇ and a density of 2.0 ⁇ 10 4 to 8.0 ⁇ 10 5 g/ It describes an invention relating to a conductive nonwoven fabric, which is m3 , and is described to have high radio wave absorption properties.
  • the conductive nonwoven fabric described in Patent Document 2 is produced by forming a metal layer on the surface of a nonwoven fabric made of organic fibers by sputtering or the like, and the formed metal layer is an extremely thin layer. Therefore, the conductive nonwoven fabric has a problem that the resistance value is easily changed by compression.
  • a thermally conductive sheet is placed between a heat generating body and a heat dissipating body in a compressed manner so that the heat generated from the heat generating body is transmitted to the heat dissipating body and radiated.
  • the resistance value changes due to compression, resulting in a decrease in electromagnetic wave absorption performance. From this point of view, it is an object of the present invention to provide an electromagnetic wave absorbing sheet that has excellent thermal conductivity and electromagnetic wave absorbing property, and whose electromagnetic wave absorbing performance does not easily deteriorate even when compressed.
  • the present inventor has made extensive studies to solve the above problems. As a result, it has a laminated structure comprising a first thermally conductive layer and a second thermally conductive layer in which an electromagnetic wave absorbing member having through holes is impregnated with a thermally conductive material.
  • the inventors have found that the above problems can be solved by an electromagnetic wave absorbing sheet having a specific range of the ratio (R1/R2) of the resistance value R1 in the no-load state to the value R2, and completed the present invention. That is, the present invention provides the following [1] to [6].
  • a laminated structure comprising a first thermally conductive layer and a second thermally conductive layer laminated on the first thermally conductive layer, the second thermally conductive layer having through holes It is a layer in which an electromagnetic wave absorbing member is impregnated with a thermally conductive material, and the resistance value ratio (R1/R2) of the resistance value R1 in a no-load state to the resistance value R2 in a 50% compressed state is given by the following formula.
  • An electromagnetic wave absorbing sheet that satisfies (1).
  • an electromagnetic wave absorbing sheet that has excellent thermal conductivity and electromagnetic wave absorbing properties, and whose electromagnetic wave absorbing performance does not easily decrease even when compressed.
  • FIG. 4 is a diagram schematically showing a method of measuring resistance values R1 and R2;
  • the electromagnetic wave absorbing sheet of the present invention has a laminated structure comprising a first heat conductive layer and a second heat conductive layer laminated on the first heat conductive layer, and the second heat conductive layer is , a layer in which an electromagnetic wave absorbing member having through holes is impregnated with a thermally conductive material, and the ratio (R1/R2) of the resistance value R1 in a no-load state to the resistance value R2 in a 50% compressed state is It satisfies the following formula (1). 0.65 ⁇ R1/R2 ⁇ 0.99 Formula (1)
  • the electromagnetic wave absorbing sheet 10 of the present invention has a laminated structure comprising a first heat conductive layer 11 and a second heat conductive layer 12 laminated on the first heat conductive layer 11 .
  • the second heat conductive layer 12 is a layer in which an electromagnetic wave absorbing member 13 having through holes is impregnated with a heat conductive material.
  • the ratio (R1/R2) of the resistance value R1 under no load to the resistance value R2 under 50% compression of the electromagnetic wave absorbing sheet 10 is set to more than 0.65 to 0. By making it less than 0.99, the deterioration of the electromagnetic wave absorption performance at the time of compression is suppressed.
  • the first thermally conductive layer 11 contains a polymer matrix 18 and an anisotropic filler 19 , specifically the anisotropic filler 19 dispersed in the polymer matrix 18 .
  • the anisotropic filler 19 is oriented in the thickness direction of the first thermally conductive layer 11 , thereby improving the thermal conductivity of the electromagnetic wave absorbing sheet 10 .
  • an anisotropic filler 20 is blended with the anisotropic filler 19 in the first thermally conductive layer. Thereby, the thermal conductivity of the electromagnetic wave absorbing sheet 10 is further improved.
  • FIG. 1 shows a mode in which the non-anisotropic filler 20 is blended, the non-anisotropic filler 20 may not be blended in the first heat conductive layer. That is, the first thermally conductive layer 11 may be in a mode in which only the anisotropic filler 19 is blended as the filler.
  • the second heat conductive layer 12 is a layer in which the electromagnetic wave absorbing member 13 having through holes is impregnated with a heat conductive material.
  • the thermally conductive material is a material containing a polymer matrix 16 and an insulating filler 17 , more specifically, a material in which the insulating filler 17 is dispersed in the polymer matrix 16 . Since the second heat conductive layer contains the insulating filler 17, the electromagnetic wave absorbing member 13 is provided with a certain level of insulating properties, and can be suitably used for electronic devices and the like.
  • the electromagnetic wave absorbing member 13 Since the second thermally conductive layer 12 has a structure impregnated with a thermally conductive material, the electromagnetic wave absorbing member 13 is reinforced, and furthermore, the adhesion with the first thermally conductive layer is enhanced, and each layer is peeled off. It is possible to prevent problems such as
  • the electromagnetic wave absorbing member 13 has a metal layer (not shown) on at least one surface 13a, which enhances the electromagnetic wave absorbing performance of the electromagnetic wave absorbing sheet 10. As shown in FIG.
  • the electromagnetic wave absorbing member 13 is preferably a conductive nonwoven fabric having a metal layer on at least one surface of the nonwoven fabric. It is preferable that the metal layer is provided on the surface of the electromagnetic wave absorbing member opposite to the surface facing the first heat conductive layer.
  • the second thermally conductive layer 12 includes, from the side close to the first thermally conductive layer, an internal insulating layer 14 containing a polymer matrix 16 and insulating fillers 17, a polymer matrix 16 and insulating fillers 17 in through-holes.
  • An electromagnetic wave absorbing member 13 including a polymer matrix 16 and a surface insulating layer 15 including an insulating filler 17 are arranged in layers.
  • the internal insulating layer 14 can prevent conduction between the first heat conductive layer 11 and the electromagnetic wave absorbing member 13 .
  • the resistance value ratio (R1/R2) of the resistance value R1 under no load to the resistance value R2 under 50% compression satisfies the following formula (1). 0.65 ⁇ R1/R2 ⁇ 0.99 Expression (1) If the electromagnetic wave absorbing sheet does not satisfy the resistance value ratio (R1/R2) of formula (1), the electromagnetic wave absorbing performance tends to decrease when compressed.
  • the resistance value ratio (R1/R2) of the electromagnetic wave absorbing sheet is preferably 0.75 or more, more preferably 0.80 or more, still more preferably 0.85 or more, and preferably 0.95 or less. is.
  • the range of the resistance value ratio (R1/R2) of the electromagnetic wave absorbing sheet is preferably 0.75 to 0.95, more preferably 0.80 to 0.95, still more preferably 0.85 to 0.95.
  • the resistance value R1 and the resistance value R2 of the electromagnetic wave absorbing sheet are not particularly limited, they are, for example, 10 to 100 ⁇ .
  • the resistance value R1 and the resistance value R2 are each measured by a non-contact resistance measuring device.
  • the range indicated by "-" means a range from a predetermined numerical value or more to a predetermined numerical value or less described before and after "-".
  • FIG. 2 shows a diagram schematically showing a method of measuring the resistance values R1 and R2.
  • two restraining plates 21 material: polycarbonate resin, thickness: 3 mm
  • spacers 23 and screws 22 are used to hold the two restraining plates 21 together. are fixed at regular intervals.
  • the resistance value of the electromagnetic wave absorbing sheet 10 is measured by an eddy current method using a probe 24 provided on the upper restraining plate 21 .
  • the electromagnetic wave absorbing sheet 10 is arranged so that the second heat conductive layer side faces the probe 24 side.
  • the resistance value R1 is obtained by measuring the resistance value of the electromagnetic wave absorbing sheet 10 in an unloaded state (a state in which the pressing plate 21 on the upper surface side receives the load but is not substantially compressed).
  • the resistance value R2 is measured by compressing the electromagnetic wave absorbing sheet 10 by 50% (that is, by compressing it to 50% of its original thickness).
  • the resistance values R1 and R2 are converted values shown by the formulas (5a) and (5b) with respect to the resistance values Rs1 and Rs2 measured through a 3 mm presser plate.
  • the resistance value Rs1 is the resistance value measured by the method shown in FIG. 2 with the electromagnetic wave absorbing sheet 10 under no load
  • the resistance value Rs2 is shown in FIG. 2 when the electromagnetic wave absorbing sheet 10 is compressed by 50%.
  • the resistance value R1 and the resistance value R2 are the values obtained by calculating the resistance value directly measured without using the 3 mm presser plate based on the formulas (5a) and (5b). That is, for three nonwoven fabrics having different known resistance values in advance, the resistance value directly measured without using a presser plate and the resistance value measured in an uncompressed state through a 3 mm presser plate are plotted on the horizontal axis. is the resistance value measured through a 3mm presser plate, and the vertical axis is the resistance value directly measured. demand. Then, the resistance values R1 and R2 were calculated from the obtained measured values using a conversion formula.
  • the non-contact resistance measuring device for example, "EC-80P" manufactured by Napson Co., Ltd. can be used.
  • the electromagnetic wave absorbing sheet of the present invention has a compressibility C1 of the first heat conductive layer when pressed from the first heat conductive layer side of the electromagnetic wave absorbing sheet with a ⁇ 3 mm pusher with a load of 400 g, and a first heat It is preferable that the thickness T1 of the conductive layer and the thickness T2 of the second thermally conductive layer satisfy the following formula (2).
  • the electromagnetic wave absorbing sheet satisfies the formula (2), that is, C1 ⁇ T1 / (T1 + T2) is more than 0.26, so that the resistance value ratio (R1 / R2) described above is the desired value represented by the formula (1) It becomes easy to adjust within the range, and it is possible to suppress deterioration of the electromagnetic wave absorbing performance when the electromagnetic wave absorbing sheet is compressed.
  • C1 ⁇ T1/(T1+T2) is preferably 0.50 or more, more preferably 0.60 or more, and preferably 1.0 or less.
  • C1 ⁇ T1/(T1+T2) is preferably 0.50 to 1.0, more preferably 0.60 to 1.0.
  • the first thermally conductive layer is relatively hard, the thickness of the first thermally conductive layer must be increased. , the first heat-conducting layer needs to be softened.
  • the thickness T1 of the first thermally conductive layer and the thickness T2 of the second thermally conductive layer in the formula (2) are the thicknesses of the respective thermally conductive layers before the electromagnetic wave absorbing sheet is pressed with a pusher. means.
  • C1 in Equation (2) is the compressibility of the first heat conductive layer, and the thickness T1 of the first heat conductive layer before pressing with the plunger and the thickness T1 after pressing with the plunger.
  • the thickness T1' of the first heat conductive layer in the cut portion is obtained by the following equation (3).
  • C1 (T1-T1')/T1 formula (3)
  • the compressibility C1 is preferably 0.20-0.95, more preferably 0.55-0.90. When the compression rate C1 is within such a range, it becomes easier to satisfy the formula (2).
  • the compressibility can be adjusted by adjusting the type of polymer matrix forming the thermally conductive layer, the amount of filling material (filler), and the like.
  • the thickness T1 of the first heat conductive layer is not particularly limited, but from the viewpoint of suppressing the deterioration of the electromagnetic wave absorption performance when the electromagnetic wave absorbing sheet is compressed, and from the viewpoint of suppressing the deterioration of the electromagnetic wave absorption performance when compressed, it is preferably 0. 0.2 mm or more, more preferably 1 mm or more, and still more preferably 1.2 mm or more.
  • the thickness T1 of the first heat conductive layer is not particularly limited, but from the viewpoint of improving the heat conductivity of the electromagnetic wave absorbing sheet, it is preferably 5 mm or less, more preferably 3 mm or less, and still more preferably 2 mm or less. is.
  • the thickness T1 of the first heat conductive layer is not particularly limited, but from the viewpoint of improving the heat conductivity of the electromagnetic wave absorbing sheet and suppressing the deterioration of the electromagnetic wave absorbing performance during compression, it is preferably 0.2 to 5 mm. , more preferably 1 to 3 mm, still more preferably 1.2 to 2 mm.
  • the thickness T2 of the second heat conductive layer is not particularly limited, it is preferably 0.05 mm or more, more preferably 0.08 mm or more, from the viewpoint of suppressing deterioration of electromagnetic wave absorption performance when the electromagnetic wave absorbing sheet is compressed. Yes, more preferably 0.1 mm or more.
  • the thickness T2 of the second heat conductive layer is not particularly limited, but from the viewpoint of improving the heat conductivity of the electromagnetic wave absorbing sheet, it is preferably 3 mm or less, more preferably 2 mm or less, and still more preferably 1 mm or less. is.
  • the thickness T2 of the second heat conductive layer is not particularly limited, but from the viewpoint of improving the heat conductivity of the electromagnetic wave absorbing sheet and suppressing the deterioration of the electromagnetic wave absorbing performance during compression, it is preferably 0.05 to 3 mm. , more preferably 0.08 to 2 mm, still more preferably 0.1 to 1 mm. From the viewpoint of easily satisfying Expression (2), it is preferable to make the thickness T2 of the second thermally conductive layer thinner than the thickness T1 of the first thermally conductive layer.
  • the compressibility C2 of the second heat conductive layer when the second heat conductive layer side of the electromagnetic wave absorbing sheet is pressed with a load of 400 g by a pusher of ⁇ 3 mm is preferably 0.10 to 0.90, More preferably 0.30 to 0.80.
  • the compression rate C2 is preferably a value smaller than the compression rate C1 described above.
  • the electromagnetic wave absorbing sheet of the present invention comprises a first heat conductive layer.
  • the first thermally conductive layer contains an anisotropic filler oriented in the thickness direction of the thermally conductive layer, thereby having high thermal conductivity and improving the heat dissipation of the electromagnetic wave absorbing sheet.
  • First thermally conductive layer 11 contains polymer matrix 18 and anisotropic filler 19 .
  • the first thermally conductive layer may further contain a non-anisotropic filler 20 .
  • the state in which the anisotropic filler is oriented means that the major axis directions of the anisotropic filler are aligned in a predetermined direction.
  • the polymer matrix 18 used in the first heat conductive layer 11 is a polymer compound such as elastomer or rubber, preferably a liquid polymer composition (curing agent) composed of a mixed system such as a main agent and a curing agent. polymer composition) is preferably used.
  • the curable polymer composition may comprise, for example, uncrosslinked rubber and a cross-linking agent, or may comprise a monomer, prepolymer, etc. and a curing agent. Further, the curing reaction may be room temperature curing or heat curing.
  • a polymer matrix formed from a curable polymer composition is preferably silicone rubber.
  • silicone rubber addition reaction-curable silicone is preferably used as the polymer matrix (curable polymer composition).
  • a curable polymer composition containing an alkenyl group-containing organopolysiloxane and a hydrogen organopolysiloxane may be used.
  • the rubber various synthetic rubbers can be used in addition to the above. rubber, butyl rubber, and the like.
  • the synthetic rubber may be crosslinked or left uncrosslinked (ie, uncured) in the first thermally conductive layer. Uncrosslinked rubber is mainly used in flow orientation.
  • crosslinked (that is, cured) as described above, the polymer matrix is obtained by curing a curable polymer composition comprising an uncrosslinked rubber made of these synthetic rubbers and a crosslinking agent. And it is sufficient.
  • thermoplastic elastomers such as polyester-based thermoplastic elastomers and polyurethane-based thermoplastic elastomers, and thermosetting elastomers formed by curing a mixed liquid polymer composition consisting of a main agent and a curing agent are also used as elastomers.
  • a polyurethane-based elastomer formed by curing a polymer composition containing a polymer having a hydroxyl group and an isocyanate can be exemplified.
  • silicone rubbers especially addition reaction-curing silicones, are preferred because the polymer matrix after curing is particularly flexible and the anisotropic and non-anisotropic fillers can be easily filled. is preferred.
  • the polymer composition for forming the polymer matrix may consist of a polymer compound alone, or may consist of a polymer compound and a plasticizer.
  • a plasticizer is preferably used when synthetic rubber is used, and by including a plasticizer, it is possible to increase the flexibility of the polymer matrix when it is not crosslinked.
  • the plasticizer those having compatibility with the polymer compound are used, and specifically, ester plasticizers and silicone oils are preferred.
  • ester plasticizers include phthalates, adipates, trimellitates, phosphates, sebacates, azelates, maleates, and benzoates.
  • Silicone oils include polydimethylsiloxane.
  • its content is preferably 1 to 30% by volume, more preferably 5 to 20% by volume, relative to the total amount of the first heat conductive layer.
  • the content of the polymer matrix is preferably 15-50% by volume, more preferably 20-45% by volume, relative to the total amount of the first heat conductive layer.
  • the anisotropic filler 19 mixed in the polymer matrix 18 is a filler having an anisotropic shape, and is an orientable filler.
  • the anisotropic filler 19 is a thermally conductive filler. Examples of the anisotropic filler 19 include fibrous materials and scaly materials.
  • the anisotropic filler 19 has a high aspect ratio, specifically an aspect ratio exceeding 2, preferably 5 or more. By making the aspect ratio larger than 2, the anisotropic filler 19 can be easily oriented in the thickness direction, and the thermal conductivity of the first thermally conductive layer can be easily increased.
  • the upper limit of the aspect ratio is not particularly limited, but is practically 100.
  • the aspect ratio is preferably more than 2 and 100 or less, more preferably 5-100.
  • the aspect ratio is the ratio of the length of the anisotropic filler 19 in the long axis direction to the length of the short axis direction. means the longitudinal length/thickness of the scaly material.
  • the anisotropic filler 19 is preferably a fibrous material from the viewpoint of increasing thermal conductivity.
  • the content of the anisotropic filler 19 in the first thermally conductive layer 11 is preferably 5 to 35% by volume, more preferably 8 to 30% by volume, relative to the total amount of the first thermally conductive layer.
  • the anisotropic filler 19 is a fibrous material
  • its average fiber length is preferably 50-500 ⁇ m, more preferably 70-350 ⁇ m.
  • the anisotropic fillers are appropriately brought into contact with each other inside the first heat conductive layer 11 to ensure a heat transfer path.
  • the average fiber length is 500 ⁇ m or less, the bulk of the anisotropic filler becomes low, and high filling into the polymer matrix becomes possible.
  • said average fiber length can be calculated by observing an anisotropic filler with a microscope. More specifically, for example, using an electron microscope or an optical microscope, the fiber length of 50 arbitrary anisotropic fillers is measured, and the average value (arithmetic mean value) can be taken as the average fiber length. can.
  • the average fiber length of the fiber material is preferably shorter than the thickness of the first heat conductive layer 11 . Being shorter than the thickness prevents the fibrous material from protruding more than necessary from the surface of the first heat conductive layer 11 .
  • the anisotropic filler 19 is a scale-like material, the average particle diameter thereof is preferably 5 to 300 ⁇ m, more preferably 10 to 100 ⁇ m. Moreover, 10 to 50 ⁇ m is particularly preferable. By setting the average particle diameter to 5 ⁇ m or more, the anisotropic fillers 19 easily come into contact with each other in the first heat conductive layer, thereby ensuring a heat transfer path.
  • the average particle size of the scaly material can be calculated by observing the anisotropic filler with a microscope and taking the major axis as the diameter. More specifically, for example, using an electron microscope or an optical microscope, the major diameters of 50 arbitrary anisotropic fillers are measured, and the average value (arithmetic average value) can be taken as the average fiber length. .
  • the anisotropic filler 19 may be made of a known thermally conductive material, but preferably has diamagnetism so that it can be magnetically oriented as described later.
  • Specific examples of the anisotropic filler 19 include carbon-based materials such as carbon fibers or scale-like carbon powder, metal materials and metal oxides such as metal fibers, boron nitride, metal nitrides, and metal carbides. , metal hydroxides, and the like.
  • carbon-based materials are preferred because of their small specific gravity and good dispersibility in the polymer matrix 12.
  • graphitized carbon materials with high thermal conductivity are more preferred.
  • the graphitized carbon material has diamagnetism when the graphite planes are aligned in a predetermined direction.
  • Boron nitride or the like also has diamagnetism when the crystal planes are aligned in a predetermined direction.
  • it is particularly preferable that the anisotropic filler 19 is carbon fiber.
  • the anisotropic filler 19 is not particularly limited, but generally has a thermal conductivity of 60 W/m ⁇ K or more, preferably 400 W, along the anisotropic direction (that is, the longitudinal direction). /m ⁇ K or more. Although the upper limit of the thermal conductivity of the anisotropic filler 19 is not particularly limited, it is, for example, 2000 W/m ⁇ K or less.
  • the method for measuring thermal conductivity is the laser flash method.
  • the anisotropic filler 19 may be used singly or in combination of two or more.
  • anisotropic fillers 19 having at least two different average particle sizes or average fiber lengths may be used as the anisotropic fillers 19 .
  • the use of anisotropic fillers of different sizes allows the anisotropic fillers to be densely packed into the polymer matrix by intercalating smaller anisotropic fillers between relatively larger anisotropic fillers. It is thought that it can be filled and the efficiency of heat conduction can be improved.
  • Carbon fibers used as the anisotropic filler 19 are preferably graphitized carbon fibers.
  • flake-like graphite powder is preferable.
  • the anisotropic filler 19 is more preferably graphitized carbon fiber.
  • Graphitized carbon fibers have graphite crystal planes aligned in the fiber axis direction, and have high thermal conductivity in the fiber axis direction. Therefore, by aligning the fiber axis directions in a predetermined direction, the thermal conductivity in a specific direction can be increased.
  • the crystal planes of graphite are continuous in the in-plane direction of the flake surface, and the in-plane direction has a high thermal conductivity. Therefore, by aligning the scale surfaces in a predetermined direction, it is possible to increase the thermal conductivity in a specific direction.
  • Graphitized carbon fibers and flake graphite powder preferably have a high degree of graphitization.
  • the graphitized carbon material such as the graphitized carbon fiber and flake graphite powder
  • the following materials obtained by graphitizing can be used.
  • condensed polycyclic hydrocarbon compounds such as naphthalene, PAN (polyacrylonitrile), condensed heterocyclic compounds such as pitch, etc.
  • graphitized mesophase pitch, polyimide, and polybenzazole which have a particularly high degree of graphitization, can be used. is preferred.
  • mesophase pitch in the spinning process described later, the pitch is oriented in the fiber axis direction due to its anisotropy, and graphitized carbon fibers having excellent thermal conductivity in the fiber axis direction can be obtained.
  • the mode of use of the mesophase pitch in the graphitized carbon fiber is not particularly limited as long as it can be spun, and the mesophase pitch may be used alone or in combination with other raw materials.
  • the use of mesophase pitch alone that is, graphitized carbon fiber with a mesophase pitch content of 100% is most preferable from the viewpoint of high thermal conductivity, spinnability and quality stability.
  • the graphitized carbon fiber can be obtained by sequentially performing spinning, infusibilization, and carbonization, pulverizing or cutting into a predetermined particle size and then graphitizing, or pulverizing or cutting after carbonization and graphitizing. can.
  • pulverizing or cutting before graphitization condensation polymerization reaction and cyclization reaction tend to proceed during graphitization on the surface newly exposed by pulverization, so the degree of graphitization is increased and heat conduction is further improved.
  • a graphitized carbon fiber with improved properties can be obtained.
  • the spun carbon fibers are graphitized and then pulverized, the graphitized carbon fibers are rigid and easy to pulverize, and a carbon fiber powder having a relatively narrow fiber length distribution can be obtained by pulverization in a short time.
  • the anisotropic filler 19 is oriented in the thickness direction as described above. It shall be oriented in the thickness direction even if it is tilted. Specifically, an anisotropic filler 19 whose long axis direction is inclined by about less than 20° is also oriented in the thickness direction, and such an anisotropic filler 19 is the first thermal conductive material. In a layer, if predominant (for example greater than 60%, preferably greater than 80% relative to the total number of anisotropic fillers), it shall be oriented in the thickness direction.
  • the non-anisotropic filler 20 is a thermally conductive filler contained in the first thermally conductive layer separately from the anisotropic filler 19, and is included in the first thermally conductive layer together with the anisotropic filler 19. It is a material that imparts thermal conductivity. In addition, it is difficult to increase the contact area between the anisotropic fillers 19 when the fiber length is increased, for example, but by filling the gap with the non-anisotropic filler 20, a heat transfer path can be formed. A first thermally conductive layer having a high thermal conductivity is obtained.
  • the non-anisotropic filler 20 is a filler that does not substantially have anisotropy in shape, and the anisotropic filler 19 is oriented in a predetermined direction under the generation of magnetic lines of force or the action of a shearing force, which will be described later. It is a filler that is not oriented in the predetermined direction even under the environment.
  • the non-anisotropic filler 20 has an aspect ratio of 2 or less, preferably 1.5 or less.
  • the thermally conductive filler is appropriately interposed in the gaps between the anisotropic fillers 19, and the heat is conducted.
  • a first thermally conductive layer with a high modulus is obtained.
  • the aspect ratio is set to 2 or less, it is possible to prevent the viscosity of the first thermally conductive layer composition described later from increasing and to achieve high filling.
  • non-anisotropic filler 20 examples include metals, metal oxides, metal nitrides, metal hydroxides, carbon materials, oxides other than metals, nitrides, and carbides.
  • shape of the non-anisotropic filler 20 may be spherical or amorphous powder.
  • metals such as aluminum, copper, and nickel; metal oxides such as aluminum oxide, magnesium oxide, and zinc oxide represented by alumina; and metal nitrides such as aluminum nitride. can be exemplified.
  • Metal hydroxides include aluminum hydroxide.
  • spherical graphite etc. are mentioned as a carbon material.
  • the non-anisotropic filler 20 is preferably one or more selected from the group consisting of alumina, aluminum, aluminum hydroxide, zinc oxide, boron nitride, and aluminum nitride among those mentioned above. It is more preferably one or more selected from the group consisting of aluminum hydroxide. As the non-anisotropic filler 20, one of the above-described fillers may be used alone, or two or more thereof may be used in combination.
  • the average particle size of the non-anisotropic filler 20 is preferably 0.1-50 ⁇ m, more preferably 0.5-35 ⁇ m. Moreover, it is particularly preferable to be 1 to 20 ⁇ m. By setting the average particle diameter to 50 ⁇ m or less, problems such as disturbing the orientation of the anisotropic filler 19 are less likely to occur. In addition, by setting the average particle size to 0.1 ⁇ m or more, the specific surface area of the non-anisotropic filler 20 does not become unnecessarily large, and the viscosity of the first heat conductive layer composition can be reduced even if a large amount is blended. is less likely to rise, making it easier to fill the non-anisotropic filler 20 at a high rate.
  • Non-anisotropic fillers 20 may be used, for example, as non-anisotropic fillers 20, non-anisotropic fillers 20 having at least two mutually different average particle sizes.
  • the average particle size of the non-anisotropic filler 20 can be measured by observing with an electron microscope or the like. More specifically, for example, using an electron microscope or an optical microscope, the particle size of 50 arbitrary non-anisotropic fillers is measured, and the average value (arithmetic average value) is taken as the average particle size. can be done.
  • the content of the non-anisotropic filler 20 is preferably 30-60% by volume, more preferably 35-55% by volume, relative to the total amount of the first heat conductive layer.
  • the content of the non-anisotropic filler 20 is preferably 30-60% by volume, more preferably 35-55% by volume, relative to the total amount of the first heat conductive layer.
  • the polymer matrix 18 may further contain various additives within a range that does not impair the function of the first thermally conductive layer.
  • the additive include at least one selected from dispersants, coupling agents, adhesives, flame retardants, antioxidants, colorants, anti-settling agents and the like.
  • additives such as a crosslinking accelerator and a curing accelerator that promote crosslinking and curing may be added.
  • the type E hardness defined by JIS K6253 of the first heat conductive layer 11 is preferably 15 or higher, more preferably 17 or higher, and even more preferably 18 or higher. Furthermore, the type E hardness of the first thermally conductive layer 11 is preferably 70 or less, more preferably 65 or less, even more preferably 60 or less. Also, the type E hardness of the first thermally conductive layer 11 is preferably 15-70, more preferably 17-65, even more preferably 18-60. When the type E hardness of the first heat conductive layer is not more than these upper limits, the flexibility of the first heat conductive layer is improved, and it becomes easier to suppress the deterioration of the electromagnetic wave absorption performance when the electromagnetic wave absorbing sheet is compressed. . When the type E hardness of the first thermally conductive layer is at least these lower limits, the first thermally conductive layer can be easily manufactured.
  • the first thermally conductive layer is not particularly limited, but can be manufactured, for example, by a method including the following steps (A) and (B).
  • an oriented molded body is formed from a first thermally conductive layer composition containing an anisotropic filler and a polymer composition as a raw material for a polymer matrix.
  • the first thermally conductive layer composition may further contain a non-anisotropic filler.
  • the composition for the first thermally conductive layer is preferably cured to form an oriented molding. More specifically, the oriented compact can be obtained by a magnetic orientation method or a flow orientation method, and among these, the magnetic orientation method is preferred.
  • a first thermally conductive layer composition containing a liquid polymer composition that will form a polymer matrix after curing, an anisotropic filler and, if necessary, a non-anisotropic filler is coated with gold.
  • the polymer composition After being injected into a mold or the like and placed in a magnetic field to orient the anisotropic filler along the magnetic field, the polymer composition is cured to obtain an oriented compact. It is preferable to use a block-shaped oriented compact.
  • a release film may be placed in the portion of the mold that comes into contact with the first thermally conductive layer composition.
  • the release film for example, a resin film having good release properties or a resin film having one side treated with a release agent or the like is used. By using the release film, the oriented molded article can be easily released from the mold.
  • the viscosity of the first heat conductive layer composition used in the magnetic field orientation manufacturing method is preferably 10 to 300 Pa ⁇ s for magnetic field orientation.
  • the viscosity is 10 Pa ⁇ s or more, the anisotropic filler and the non-anisotropic filler are less likely to settle. Further, when the viscosity is 300 Pa ⁇ s or less, the fluidity is improved, the anisotropic filler is appropriately oriented by the magnetic field, and problems such as the orientation taking too much time do not occur.
  • the viscosity is the viscosity measured at 25° C. and a rotational speed of 10 rpm using a rotational viscometer (Brookfield viscometer DV-E, spindle SC4-14).
  • the viscosity of the first thermally conductive layer composition is 10 Pa. * It is good also as less than s.
  • a superconducting magnet, a permanent magnet, an electromagnet, etc. can be mentioned as a magnetic force line generation source for applying magnetic force lines, but a superconducting magnet is preferable in that it can generate a magnetic field with a high magnetic flux density.
  • the magnetic flux density of the magnetic field generated from these magnetic force line sources is preferably 1 to 30 Tesla.
  • the polymer composition may be cured by heating, for example, at a temperature of about 50 to 150.degree. Also, the heating time is, for example, about 10 minutes to 3 hours.
  • flow orientation manufacturing method In the flow orientation manufacturing method, a shearing force is applied to the composition for the first heat conductive layer to produce a preliminary sheet in which the anisotropic filler is oriented in the plane direction, and a plurality of these sheets are laminated to form a laminated block. It is preferable to manufacture and use the laminated block as an oriented compact. More specifically, in the flow orientation manufacturing method, first, an anisotropic filler, optionally a non-anisotropic filler, and various additives are mixed into a polymer composition and stirred to form a mixed solid. A homogeneously dispersed first thermal conductive layer composition is prepared.
  • the polymer compound used in the polymer composition may contain a polymer compound that is liquid at room temperature (23° C.) or a polymer compound that is solid at room temperature. good too.
  • the polymer composition may contain a plasticizer.
  • the composition for the first thermally conductive layer has a relatively high viscosity so that a shearing force is applied when it is stretched into a sheet. It is preferably 50 Pa ⁇ s.
  • a solvent is preferably added to the first thermally conductive layer composition in order to obtain the above viscosity.
  • the anisotropic filler can be oriented in the shear direction.
  • the sheet forming means for example, the composition for the first heat conductive layer is applied onto the base film by a coating applicator such as a bar coater or a doctor blade, or by extrusion molding or discharge from a nozzle, and After that, it is preferable to dry or semi-harden the composition for the first heat conductive layer, if necessary.
  • the thickness of the preliminary sheet is preferably about 50-250 ⁇ m.
  • the anisotropic filler is oriented in one direction along the plane of the sheet.
  • the composition for the first thermal conductive layer is cured as necessary by heating, ultraviolet irradiation, etc., and hot pressing or the like is performed.
  • the laminated block may be used as an oriented compact.
  • step (B) the oriented compact obtained in step (A) is cut by slicing or the like perpendicularly to the direction in which the anisotropic filler is oriented to obtain the first heat conductive layer. .
  • Slicing may be performed, for example, with a shearing blade.
  • the surface of the obtained first thermally conductive layer may be polished, if necessary. Polishing of the surface may be performed using, for example, abrasive paper.
  • Abrasive papers having an average particle size (D50) of abrasive grains of 3 to 60 ⁇ m can be used.
  • the second heat conductive layer 12 is a layer in which an electromagnetic wave absorbing member 13 having through holes is impregnated with a heat conductive material.
  • the electromagnetic wave absorbing member 13 having through holes in the present invention is a sheet-like member having electromagnetic wave absorbing performance, and is a member having through holes formed therein so that the interior of the member can be impregnated with a thermally conductive material.
  • the electromagnetic wave absorbing member 13 having through holes is preferably an electromagnetic wave absorbing member having a metal layer on at least one surface of a substrate having through holes.
  • fabrics such as woven fabrics, non-woven fabrics, and knitted fabrics are preferable.
  • a conductive woven fabric having a metal layer on at least one side of the woven fabric, a conductive nonwoven fabric having a metal layer on at least one side of the nonwoven fabric, and a knitted fabric having a metal layer on at least one side A conductive knitted fabric can be exemplified.
  • a conductive nonwoven fabric having a metal layer on at least one side of the nonwoven fabric and a conductive knitted fabric having a metal layer on at least one side of the knitted fabric are more preferable.
  • the conductive nonwoven fabric in the present invention preferably has a sheet resistance of 10 ⁇ / ⁇ or more, more preferably 15 ⁇ / ⁇ or more, and still more preferably 20 ⁇ / ⁇ or more on at least one surface.
  • the sheet resistance of at least one surface of the conductive nonwoven fabric is preferably 100 ⁇ / ⁇ or less, more preferably 50 ⁇ / ⁇ or less, and still more preferably 30 ⁇ / ⁇ or less.
  • the conductive nonwoven fabric in the present invention preferably has a sheet resistance on at least one side of 10 to 100 ⁇ / ⁇ , more preferably 15 to 50 ⁇ / ⁇ , and still more preferably 20 to 30 ⁇ / ⁇ . .
  • the sheet resistance of the conductive nonwoven fabric is in such a range, the low reflectivity of electromagnetic waves is improved, and the electromagnetic wave absorption performance is enhanced.
  • the sheet resistance is the surface resistance value on the surface of the metal layer side of the conductive nonwoven fabric, and is measured using a surface resistance meter (for example, manufactured by MITUBISHI CHEMICAL ANALYTECH (trade name: Loresta-EP), or its equivalent). It can be measured by the 4-probe method.
  • An ESP probe (MCP-TP08P or its equivalent) is used for the measurement, and the measurement is performed by uniformly pressing all the pins of the probe against the sample.
  • the nonwoven fabric that constitutes the conductive nonwoven fabric is not particularly limited as long as it is composed of fibers.
  • the nonwoven fabric may contain components, substances, etc. other than fibers as long as the effects of the present invention are not significantly impaired.
  • the total amount of fibers in the nonwoven fabric 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 layer structure of the nonwoven fabric is not particularly limited.
  • the nonwoven fabric may be composed of a single type of nonwoven fabric, or may be a combination of two or more types of nonwoven fabrics.
  • the material constituting the fiber is not particularly limited as long as it is fibrous or can be formed into fibrous form.
  • fiber materials include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate, polyester resins such as modified polyester, polyethylene (PE) resin, polypropylene (PP) resin, polystyrene resin, and cyclic olefin resin.
  • Polyolefin resins such as resins, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, polyvinyl acetal resins such as polyvinyl butyral (PVB), polyether ether ketone (PEEK) resins, polysulfone (PSF) resins, polyether sulfones (PES) resin, polycarbonate (PC) resin, polyamide resin, polyimide resin, acrylic resin, triacetyl cellulose (TAC) resin, polyarylate (PAR) resin, synthetic resin such as liquid crystal polymer (LCP), natural resin, cellulose, Glass etc. are mentioned.
  • PVB polyvinyl butyral
  • PEEK polyether ether ketone
  • PSF polysulfone
  • PES polyether sulfones
  • PC polycarbonate
  • PC polyamide resin
  • polyimide resin acrylic resin
  • TAC triacetyl cellulose
  • PAR polyarylate
  • synthetic resin such as liquid crystal polymer (
  • the fiber material may be composed of a single type of fiber material, or may be a combination of two or more types of fiber material.
  • the basis weight (basis weight) of the nonwoven fabric is, for example, 0.5 to 200 g/m 2 , preferably 0.5 to 50 g/m 2 , more preferably 1 to 10 g/m 2 .
  • the thickness of the nonwoven fabric is, for example, 1-500 ⁇ m, preferably 5-100 ⁇ m, more preferably 10-30 ⁇ m. When the basis weight and thickness of the nonwoven fabric are within such ranges, it becomes easier to adjust the density within the range described below.
  • the density of the nonwoven fabric is preferably 2.0 ⁇ 10 4 to 8.0 ⁇ 10 5 g/m 3 , more preferably 5.0 ⁇ 10 4 to 6.0 ⁇ 10 5 g/m 3 , More preferably, it is 1.0 ⁇ 10 5 to 5.0 ⁇ 10 5 g/m 3 .
  • the density of the nonwoven fabric is within such a range, it becomes easier to absorb electromagnetic waves, and the electromagnetic wave absorption performance is enhanced. It is not clear why the electromagnetic wave absorption performance increases when the density of the nonwoven fabric is in the above range, but by using a nonwoven fabric with a density within a specific range, the metal does not adhere only to the surface of the nonwoven fabric, but to the inside of the nonwoven fabric. It is thought that the radio wave absorption characteristics (especially absorbability) are improved because it penetrates into the
  • the conductive metal layer is a conductive nonwoven fabric having a metal layer on at least one surface of the nonwoven fabric.
  • the metal layer is not particularly limited as long as it is a layer containing metal as a material.
  • the metal layer may contain components other than metals as long as the effects of the present invention are not significantly impaired. In that case, the amount of metal in the metal layer 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 metal constituting the metal layer is not particularly limited as long as it can exhibit radio wave absorption properties.
  • metals include nickel, molybdenum, chromium, titanium, aluminum, gold, silver, copper, zinc, tin, platinum, iron, indium, alloys containing these metals, and these metals or alloys containing these metals. and the like.
  • the metal layer contains at least one metal element selected from the group consisting of nickel, molybdenum, chromium, titanium, and aluminum from the viewpoint of suppressing changes in the radio wave absorption properties of the conductive nonwoven fabric over time (durability). preferably.
  • the content is, for example, 10% by mass or more, preferably 20% by mass. Above, more preferably 40% by mass or more, still more preferably 60% by mass or more, and usually less than 100% by mass.
  • a metal layer containing molybdenum is preferably used from the viewpoint of durability and easy adjustment of sheet resistance.
  • the molybdenum content in the metal layer is preferably 5% by mass or more, more preferably 7% by mass or more, still more preferably 9% by mass or more, and still more preferably 11% by mass, from the viewpoint of further improving durability. % by mass or more, more preferably 13% by mass or more, still more preferably 15% by mass or more, and even more preferably 16% by mass or more.
  • the molybdenum content is preferably 70% by mass or less, more preferably 30% by mass or less, and still more preferably 25% by mass or less, from the viewpoint of facilitating adjustment of the surface resistance value. More preferably, it is 20% by mass or less.
  • the metal layer contains molybdenum
  • nickel and chromium in addition to molybdenum in the metal layer, a conductive nonwoven fabric having more excellent durability can be obtained.
  • alloys containing nickel, chromium and molybdenum include Hastelloy B-2, B-3, C-4, C-2000, C-22, C-276, G-30, N, W, X, etc. Various grades are mentioned.
  • the metal layer contains molybdenum, nickel and chromium
  • these contents are preferably adjusted as follows from the viewpoint of obtaining a highly durable conductive nonwoven fabric. It is preferable that the content of molybdenum is 5% by mass or more, the content of nickel is 40% by mass or more, and the content of chromium is 1% by mass or more.
  • the contents of molybdenum, nickel, and chromium are within the above ranges, a conductive nonwoven fabric having more excellent durability can be obtained. More preferably, the molybdenum, nickel and chromium contents are 7% by mass or more for molybdenum, 45% by mass or more for nickel, and 3% by mass or more for chromium.
  • the molybdenum content is 9% by mass or more, the nickel content is 47% by mass or more, and the chromium content is 5% by mass or more. More preferably, the molybdenum, nickel and chromium contents are 11% by mass or more, 50% by mass or more for nickel, and 10% by mass or more for chromium. Regarding the molybdenum, nickel and chromium contents, it is particularly preferable that the molybdenum content is 13% by mass or more, the nickel content is 53% by mass or more, and the chromium content is 12% by mass or more.
  • the molybdenum content is 15% by mass or more, the nickel content is 55% by mass or more, and the chromium content is 15% by mass or more.
  • the contents of molybdenum, nickel and chromium it is most preferable that the molybdenum content is 16% by mass or more, the nickel content is 57% by mass or more, and the chromium content is 16% by mass or more.
  • the content of nickel is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 65% by mass or less.
  • the chromium content is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less.
  • the metal layer may contain metals other than the above molybdenum, nickel and chromium.
  • metals include iron, cobalt, tungsten, manganese, titanium and the like.
  • the total content of metals other than molybdenum, nickel and chromium is preferably 45% by mass or less, more preferably 40% by mass, from the viewpoint of durability of the metal layer. Below, more preferably 35% by mass or less, still more preferably 30% by mass or less, particularly preferably 25% by mass or less, and very preferably 23% by mass or less.
  • the total content of metals other than molybdenum, nickel and chromium is, for example, 1% by mass or more.
  • the iron content is preferably 25% by mass or less, more preferably 20% by mass or less, and still more preferably 15% by mass or less, from the viewpoint of durability of the metal layer. is 1% by mass or more.
  • the metal layer contains cobalt and/or manganese, the content is preferably 5% by mass or less, more preferably 4% by mass or less, and still more preferably 3% by mass, independently from the viewpoint of durability of the metal layer. % or less, preferably 0.1 mass % or more.
  • the metal layer contains tungsten the content is preferably 8% by mass or less, more preferably 6% by mass or less, still more preferably 4% by mass or less, from the viewpoint of durability of the metal layer. It is 1% by mass or more.
  • the metal layer may contain a metalloid element such as silicon or carbon.
  • the contents of metalloid elements such as silicon and carbon in the metal layer are each independently preferably 1% by mass or less, and more preferably 0.5% by mass or less.
  • the metal layer contains one or both of a metalloid element such as silicon and carbon, the total content thereof is preferably 0.01% by mass or more.
  • the deposition amount of the elements constituting the metal layer is, for example, 5 to 200 ⁇ g/cm 2 , preferably 50 to 150 ⁇ g/cm 2 , more preferably 80 to 120 ⁇ g/cm 2 from the viewpoint of setting the sheet resistance within the desired range. .
  • the deposition amount of the elements forming the metal layer means the total deposition amount of the metal element and the metalloid element.
  • the deposition amount of the element can be obtained by fluorescent X-ray analysis. Specifically, using a scanning fluorescent X-ray analyzer (e.g., Rigaku scanning fluorescent X-ray analyzer ZSX PrimusIII+ or equivalent), the acceleration voltage is 50 kV, the acceleration current is 50 mA, and the integration time is 60 seconds.
  • a scanning fluorescent X-ray analyzer e.g., Rigaku scanning fluorescent X-ray analyzer ZSX PrimusIII+ or equivalent
  • the X-ray intensity of the K ⁇ ray of the component to be measured is measured, and the intensity at the background position as well as the peak position is measured so that the net intensity can be calculated.
  • the measured strength value can be converted to the amount of adhesion from a calibration curve prepared in advance. The same sample is analyzed 5 times, and the average value is taken as the adhesion amount.
  • the layer structure of the metal layer is not particularly limited.
  • the metal layer may be composed of a single metal layer, or may be a combination of two or more metal layers.
  • a conductive nonwoven fabric can be obtained by a method including a step of attaching a metal to the surface of the nonwoven fabric.
  • it can be obtained by a method further including a step of adhering constituent elements of the other layer to the surface of the nonwoven fabric, the surface of the metal layer, or the like.
  • the deposition can be performed by, for example, a sputtering method, a vacuum deposition method, an ion plating method, a chemical vapor deposition method, a pulsed laser deposition method, or the like.
  • the sputtering method is preferable from the viewpoint of film thickness controllability, radio wave absorption characteristics, and the like.
  • the sputtering method is not particularly limited, but examples thereof include DC magnetron sputtering, high frequency magnetron sputtering, and ion beam sputtering.
  • the sputtering apparatus may be of a batch system or a roll-to-roll system.
  • a conductive nonwoven fabric having a metal layer on one surface can be obtained by carrying out the step of attaching a metal to one surface of the nonwoven fabric. Further, by carrying out the step of attaching metal to both surfaces of the nonwoven fabric, a conductive nonwoven fabric having metal layers on both front and back surfaces can be obtained.
  • the metal layer preferably has a barrier layer on at least one side thereof, preferably on both sides.
  • the barrier layer is not particularly limited as long as it is a layer capable of protecting the metal layer and suppressing its deterioration, but it preferably has a composition different from that of the metal layer.
  • Materials for the barrier layer include, for example, metals, semimetals, alloys, metallic compounds, and semimetallic compounds.
  • 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, still more preferably 99% by mass or more, and usually less than 100% by mass. .
  • Metals suitably used for the barrier layer include, for example, nickel, titanium, aluminum, niobium, and cobalt.
  • Semimetals suitable for the barrier layer include, for example, silicon, germanium, antimony, bismuth and the like.
  • metal compounds and metalloid compounds used for the barrier layer include SiO2 , SiOx (X represents an oxidation number, 0 ⁇ X ⁇ 2), Al2O3 , MgAl2O4 , CuO, CuN, TiO 2 , TiN, AZO (aluminum-doped zinc oxide), and the like.
  • the barrier layer preferably contains at least one element selected from the group consisting of nickel, silicon, titanium and aluminum. Among these, silicon is preferred.
  • the amount of the elements forming the barrier layer is not particularly limited as long as the above-described sheet resistance can be satisfied.
  • the adhesion amount of the elements constituting the barrier layer is, for example, 0.5 to 15 ⁇ g/cm 2 , preferably 1 to 10 ⁇ g/cm 2 , more preferably 2 to 5 ⁇ g/cm 2 .
  • the deposition amount of the elements constituting the barrier layer means the total deposition amount of the metal element and the metalloid element. When the barrier layers are formed on both sides of the metal layer, the amount of the element attached to each barrier layer is preferably within the range described above.
  • the layer structure of the barrier layer is not particularly limited.
  • the barrier layer may be composed of a single barrier layer, or may be a combination of two or more barrier layers.
  • a conductive woven fabric and a conductive knitted fabric can be obtained.
  • the conductive woven fabric is highly effective in suppressing elongation in the direction of fibers forming the woven fabric, and is therefore preferable in that the shape of the electromagnetic wave absorbing member in the planar direction is less likely to deform.
  • the conductive knitted fabric is easily deformed in the planar direction, it is preferable in terms of obtaining an electromagnetic wave absorbing member having excellent conformability to, for example, a three-dimensional shape.
  • the electromagnetic wave absorbing member is hardly damaged even if it is deformed, it is suitable for applications such as covering a polar surface-shaped adherend and irregularities caused by a plurality of heating elements.
  • the second heat conductive layer 12 is composed of an electromagnetic wave absorbing member 13 and a heat conductive material impregnated into the electromagnetic wave absorbing member 13 .
  • the thermally conductive material includes polymer matrix 16 and insulating fillers 17 .
  • polymer matrix 16 As the polymer matrix 16, those described for the polymer matrix 18 in the first heat conductive layer 11 can be used without particular limitation. The same applies to the types of preferred polymer matrices, and the same applies to the polymer composition and curable polymer composition for forming the polymer matrix. That is, the polymer matrix 16 is preferably silicone rubber, and the polymer composition (curable polymer composition) forming the polymer matrix 16 is an alkenyl group-containing organopolysiloxane and a hydrogen organopolysiloxane. It is preferred to use those containing The polymeric composition for forming the polymeric matrix 16 may contain the plasticizer and silicone oil described above. The content of the polymer matrix is preferably 10-50% by volume, more preferably 25-45% by volume, based on the total amount of the thermally conductive material.
  • additives may be added to the polymer matrix 16 as long as they do not impair the function of the second heat conductive layer.
  • the additive include at least one selected from dispersants, coupling agents, adhesives, flame retardants, antioxidants, colorants, anti-settling agents and the like.
  • a cross-linking accelerator, a curing accelerator, or the like which promotes cross-linking or curing, may be added as an additive.
  • an inorganic filler having a volume resistivity of 10 6 ⁇ cm or more can be preferably used.
  • the insulating filler 17 include alumina, magnesium oxide, zinc oxide, silicon carbide, boron nitride, and aluminum nitride, among which alumina is preferred. These insulating fillers have excellent insulating properties and excellent thermal conductivity. Therefore, the second thermally conductive layer is excellent in insulating properties and thermal conductivity.
  • the insulating filler 17 has an aspect ratio of 2 or less, preferably 1.5 or less.
  • the shape of the insulating filler 17 may be spherical or amorphous powder.
  • the average particle size of the insulating filler 17 is preferably 0.1 to 200 ⁇ m, more preferably 0.3 to 100 ⁇ m, even more preferably 0.5 to 70 ⁇ m.
  • the average particle diameter of the insulating filler can be measured by observing with an electron microscope or the like. More specifically, for example, an electron microscope or an optical microscope can be used to measure the particle size of 50 arbitrary insulating fillers, and the average value (arithmetic mean value) can be taken as the average particle size.
  • the content of the insulating filler 17 in the thermally conductive material is preferably 50 to 90% by volume, more than It is preferably 55 to 75% by volume.
  • the second heat conductive layer 12 includes, from the side closer to the first heat conductive layer, the inner insulating layer 14 containing the polymer matrix 16 and the insulating filler 17, the polymer matrix 16 and the insulating filler 17.
  • An electromagnetic wave absorbing member 13 contained in a through-hole, a surface insulating layer 15 containing a polymer matrix 16 and an insulating filler 17 are arranged in layers.
  • the second heat conductive layer consists of the internal insulating layer 14 made of a heat conductive material, the electromagnetic wave absorbing member 13 containing the heat conductive material in the through holes, and the surface insulating layer 15 made of the heat conductive material in this order. It has an overlapping structure.
  • the internal insulating layer 14 can prevent conduction between the first heat conductive layer 11 and the electromagnetic wave absorbing member 13 .
  • the thickness of the inner insulating layer 14 is, for example, 1-200 ⁇ m, preferably 5-50 ⁇ m.
  • the thickness of the electromagnetic wave absorbing member 13 containing the heat conductive material in the through holes is, for example, 1 to 500 ⁇ m, preferably 5 to 100 ⁇ m, more preferably 10 to 30 ⁇ m.
  • the thickness of the surface insulating layer 15 is, for example, 20-2000 ⁇ m, preferably 50-1500 ⁇ m, more preferably 100-1000 ⁇ m.
  • the second heat conductive layer 12 preferably has a type E hardness defined by JIS K6253 of 20-100, more preferably 30-90, still more preferably 40-80.
  • type E hardness of the second heat conductive layer is within such a range, the electromagnetic wave absorbing member is appropriately protected, and deterioration of electromagnetic wave absorbing performance when the electromagnetic wave absorbing sheet is compressed can be easily suppressed.
  • the method for producing the electromagnetic wave absorbing sheet of the present invention is not particularly limited, but preferably comprises steps 1 to 3 as follows.
  • Step 1) Step of manufacturing a first heat conductive layer
  • Step 2) Step of disposing an electromagnetic wave absorbing member on one surface of the first heat conductive layer
  • Step 3) A second electromagnetic wave absorbing member on the surface of the electromagnetic wave absorbing member a step of applying a second thermally conductive layer composition for forming a thermally conductive layer;
  • Step 2 is a step of disposing an electromagnetic wave absorbing member on one surface of the first heat conductive layer obtained in Step 1.
  • the electromagnetic wave absorbing member is the above-described conductive nonwoven fabric, it is preferable to arrange the conductive nonwoven fabric so that the metal layer is on the opposite side of the first heat conductive layer.
  • Step 3 is, after step 2, a step of applying a second heat conductive layer composition for forming a second heat conductive layer on the surface of the electromagnetic wave absorbing member.
  • the second thermally conductive layer composition is a composition containing the insulating filler 17 and a polymer composition as a raw material of the polymer matrix.
  • the polymer composition is preferably a curable polymer composition containing an alkenyl group-containing organopolysiloxane and a hydrogen organopolysiloxane.
  • the viscosity of the second thermal conductive layer composition is not particularly limited, but is, for example, about 10 to 500 Pa ⁇ s.
  • the viscosity is the viscosity measured at 25° C. and a rotational speed of 10 rpm using a rotational viscometer (Brookfield viscometer DV-E, spindle SC4-14).
  • the composition for the second heat conductive layer When the composition for the second heat conductive layer is applied to the surface of the electromagnetic wave absorbing member, the composition permeates the through holes provided in the electromagnetic wave absorbing member, and after a certain period of time, the surface of the electromagnetic wave absorbing member coated with the composition and the A part of the composition seeps out from the opposite surface and reaches the surface of the first heat conductive layer.
  • the composition for the second thermally conductive layer contains a curable polymer composition
  • the second thermally conductive layer can be formed on the first thermally conductive layer by heating and curing. and an electromagnetic wave absorbing sheet is obtained.
  • the electromagnetic wave absorbing sheet of the present invention includes a first heat conductive layer and a second heat conductive layer having an electromagnetic wave absorbing member, and has excellent heat conductivity and electromagnetic wave absorbing properties. Furthermore, as described above, the electromagnetic wave absorbing sheet of the present invention does not easily deteriorate in electromagnetic wave absorbing performance even when it is compressed. Therefore, it can exhibit excellent thermal conductivity and electromagnetic wave absorption properties in applications where it is compressed and arranged between a heating element and a radiator in, for example, various electronic devices.
  • the type E hardness specified by JIS K6253 was measured from both sides of the electromagnetic wave absorbing sheet.
  • the type E hardness measured from the first heat conductive layer side (surface) is the type E hardness of the first heat conductive layer
  • the type E hardness measured from the second heat conductive layer side (surface) is the second was the type E hardness of the heat conductive layer.
  • Resistance value ratio (R1/R2) The resistance value ratio (R1/R2) of the resistance value R1 in a no-load state to the resistance value R2 in a 50% compressed state was measured using a non-contact resistance measuring device ("EC-80P" manufactured by Napson). , measured by the method described in the specification.
  • Compression ratio C1, compression ratio C2 Compressibility C1 of the first heat conductive layer when the first heat conductive layer side of the electromagnetic wave absorbing sheet is pressed with a load of 400 g with a ⁇ 3 mm pusher, and from the second heat conductive layer side of the electromagnetic wave absorbing sheet , the compressibility C2 of the second heat conductive layer when pressed with a load of 400 g by a plunger of ⁇ 3 mm was measured.
  • the ⁇ 3 mm pusher has a cylindrical shape with a tip of ⁇ 3 mm (diameter 3 mm). The measurement was performed using a digital force gauge (“ZTS-5S” manufactured by Imada) and an electric measuring stand (“MX-500N-E” manufactured by Imada).
  • the electromagnetic wave absorption rate (loss rate) of the electromagnetic wave absorbing sheet compressed by 50% was measured according to the microstrip line method based on the IEC62333 standard. Specifically, the resistance value measurement method shown in FIG. 2 was modified as follows. That is, in the resistance value measurement, the electromagnetic wave absorbing sheet was placed between two holding plates (material: polycarbonate resin, thickness: 3 mm). Instead of the formed substrate, an electromagnetic wave absorbing sheet was placed between the pressing plate and the substrate. At this time, the distance between the restraining plate and the substrate is adjusted to 50% of the initial thickness of the electromagnetic wave absorbing sheet. Further, the electromagnetic wave absorbing sheet is arranged so that the second heat conductive layer side faces the substrate side.
  • Raw materials used in Examples and Comparative Examples are as follows. (Materials for the first thermally conductive layer and the second thermally conductive layer) ⁇ Silicone A material: Contains alkenyl group-containing organopolysiloxane and a small amount of addition reaction catalyst (platinum catalyst) ⁇ Silicone B material: Contains alkenyl group-containing organopolysiloxane and hydrogen organopolysiloxane ⁇ Silicone oil: Viscosity at 25°C 1000cs ⁇ Aluminum: Shape: spherical, average particle size 3 ⁇ m ⁇ Alumina 1: shape: polyhedron, average particle size: 0.5 ⁇ m ⁇ Alumina 2: shape: polyhedron, average particle size: 3 ⁇ m ⁇ Alumina 3: shape: spherical, average particle size: 20 ⁇ m ⁇ Alumina 4: Shape: spherical, average particle size: 45 ⁇ m ⁇ Aluminum hydroxide 1: shape: crushed, average
  • Aluminum, alumina 1-4 and aluminum hydroxide 1-2 are non-anisotropic fillers. Carbon fibers 1-3 are anisotropic fillers. Alumina 1 to 4 correspond to insulating fillers.
  • the conductive nonwoven fabric used in each example and comparative example was prepared by the following method.
  • a nonwoven fabric made of polyarylate resin (PAR) having a thickness of 18 ⁇ m, a basis weight of 6 g/m 2 and a density of 3.3 ⁇ 10 5 g/m 3 was prepared.
  • the nonwoven fabric was placed in a vacuum device and evacuated to 5.0 ⁇ 10 ⁇ 4 Pa or less.
  • argon gas was introduced to set the gas pressure to 0.5 Pa, and a barrier layer 1 made of silicon (thickness 15 nm), a metal layer made of Hastelloy (108 nm), and a silicon A barrier layer 2 (15 nm) was laminated in this order to obtain a conductive nonwoven fabric having a metal layer on one surface.
  • the element deposition amount of each layer was 3.6 ⁇ g/cm 2 for the barrier layer 1, 96 ⁇ g/cm 2 for the metal layer, and 3.6 ⁇ g/cm 2 for the barrier layer 2.
  • Hastelloy is an alloy of composition: 16.4 mass% molybdenum, 55.2 mass% nickel, 18.9 mass% chromium, 5.5 mass% iron, 3.5 mass% tungsten, and 0.5 mass% silica. . Also, the sheet resistance of the conductive nonwoven fabric was 26 to 28 ⁇ / ⁇ .
  • Example 1 Each component of Formulation 1 shown in Table 1 was mixed to obtain a first heat conductive layer composition. Subsequently, the first heat conductive layer composition was injected into a mold set to have a thickness sufficiently larger than the thickness of the first heat conductive layer to be formed, and a magnetic field of 8 T was applied in the thickness direction. After orienting the carbon fibers in the thickness direction, the matrix was cured by heating at 80° C. for 60 minutes to obtain a block-shaped oriented compact. Next, the block-shaped oriented compact was sliced into sheets using a shearing blade to obtain a first heat conductive layer. A conductive nonwoven fabric was placed on one surface of the obtained first thermally conductive layer.
  • each component of Formulation 4 shown in Table 1 was mixed to prepare a second heat conductive layer composition.
  • the composition for the second thermally conductive layer is applied to the surface of the conductive nonwoven fabric on the first thermally conductive layer, penetrated into the through holes, and then heated at 80° C. for 60 minutes to form the second thermally conductive layer.
  • the matrix of the heat conductive layer composition was cured to form a second heat conductive layer to obtain an electromagnetic wave absorbing sheet. Table 2 shows the results.
  • Table 2 shows the type of formulation of the first thermally conductive layer composition and the second thermally conductive layer composition, the thickness T1 of the first thermally conductive layer, and the thickness T2 of the second thermally conductive layer.
  • An electromagnetic wave absorbing sheet was obtained in the same manner as in Example 1, except for changing as described in and 3 above. The results are shown in Tables 2 and 3.
  • the thicknesses of the internal insulating layers of Examples 1 to 19 and Comparative Examples 1 and 2 were all about the same, ranging from 20 to 30 ⁇ m.
  • the electromagnetic wave absorbing sheet of the present invention shown in each example had a resistance value ratio (R1/R2) within the range of formula (1), and exhibited good electromagnetic wave absorbing performance even when compressed.
  • the value of "C1 ⁇ T1/(T1+T2)" determined by the product of the compressibility of the first heat conductive layer and the ratio of the thickness of the first heat conductive layer is 0.5 or more. It showed excellent electromagnetic wave absorption performance.
  • the carbon fibers contained in the first thermally conductive layer in the electromagnetic wave absorbing sheet of each example are oriented in the thickness direction of the thermally conductive layer, the electromagnetic wave absorbing sheet exhibits excellent thermal conductivity.
  • the electromagnetic wave absorbing sheets of each comparative example having a resistance value ratio (R1/R2) outside the range of formula (1) showed poor electromagnetic wave absorption performance when compressed compared to the examples. .
  • REFERENCE SIGNS LIST 10 electromagnetic wave absorbing sheet 11 first heat conductive layer 12 second heat conductive layer 13 electromagnetic wave absorbing member 14 inner insulating layer 15 surface insulating layer 16 polymer matrix 17 insulating filler 18 polymer matrix 19 anisotropic filler 20 non Anisotropic filler 21 holding plate 22 screw 23 spacer 24 probe

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  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Laminated Bodies (AREA)
  • Shielding Devices Or Components To Electric Or Magnetic Fields (AREA)

Abstract

La présente invention concerne une feuille absorbant les ondes électromagnétiques dont la structure multicouche comprend une première couche thermoconductrice et une seconde couche thermoconductrice superposée à la première couche thermoconductrice : la seconde couche thermoconductrice étant obtenue par imprégnation d'un élément absorbant les ondes électromagnétiques pourvu de trous traversants avec un matériau thermoconducteur ; et le rapport de résistance (R1/R2) entre la résistance R1 à vide et la résistance R2 à l'état comprimé à 50 % satisfaisant la relation 0,65 < R1/R2 < 0,99.　La présente invention permet de fournir une feuille absorbant les ondes électromagnétiques qui possède une excellente conductivité thermique et d'excellentes propriétés d'absorption des ondes électromagnétiques, tout en étant insensible à une diminution de la performance d'absorption des ondes électromagnétiques, même si elle est comprimée.
PCT/JP2022/042433 2021-11-16 2022-11-15 Feuille absorbant les ondes électromagnétiques WO2023090326A1 (fr)

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Publication number Priority date Publication date Assignee Title
CN116937177A (zh) * 2023-07-13 2023-10-24 苏州铂韬新材料科技有限公司 一种手机nfc天线及其吸波材料的制备方法

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Publication number Priority date Publication date Assignee Title
JP2008111053A (ja) * 2006-10-31 2008-05-15 Three M Innovative Properties Co シート形成性単量体組成物、熱伝導性シート及びその製法

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008111053A (ja) * 2006-10-31 2008-05-15 Three M Innovative Properties Co シート形成性単量体組成物、熱伝導性シート及びその製法

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116937177A (zh) * 2023-07-13 2023-10-24 苏州铂韬新材料科技有限公司 一种手机nfc天线及其吸波材料的制备方法
CN116937177B (zh) * 2023-07-13 2024-04-26 苏州铂韬新材料科技有限公司 一种手机nfc天线及其吸波材料的制备方法

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