JP2008266379A - Noise-suppressing resin composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a noise-suppressing resin composite material having a light weight and little thickness dependency of the noise-suppressing effects. <P>SOLUTION: The noise-suppressing resin composite material contains (a) a resin, (b) an insulated ultrafine powder obtained by forming an insulation film on an electroconductive ultrafine powder, and (c) an electroconductive filler. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a noise suppressing resin composite material or electromagnetic wave that is mounted or applied to prevent leakage of unnecessary electromagnetic waves generated in electronic equipment, interference between internal circuits, and malfunction due to external electromagnetic waves. The present invention relates to an interference suppressing resin composite material.

  Problems related to EMI and immunity that cause electromagnetic waves to be radiated and transmitted to the outside unintentionally from communication equipment and various electronic equipment, or cause malfunction of the equipment itself due to external and internal interference, are the latest state-of-the-art and digital technologies. With the evolution of, it is increasingly shifting to the high frequency band.

  Up to now, resin composite materials filled with ferrite or soft magnetic alloy powder have been used (see, for example, Patent Document 1), but as the radio wave used increases in the UHF region of 300 MHz or higher, the magnetic permeability decreases. As a result, there arises a problem that the thickness necessary for developing the absorption characteristics increases. In addition, since the powder having a large specific gravity is highly filled, the specific gravity of the resin composite material is increased, and there is a problem that it is not particularly suitable for reducing the weight of the mobile communication device. In particular, when the thickness of the resin composite material is 300 μm or less, there arises a problem that the noise suppressing effect is lowered.

In addition, a noise suppression sheet as a composite in which a magnetic metal is deposited on the surface of a resin sheet to which a conductive filler or a dielectric filler is added has also been proposed (see, for example, Patent Document 2). Not only is the shape of the body restricted to a sheet shape, but the manufacturing process becomes complicated and the structure becomes complicated and the noise suppression effect becomes unstable. For this reason, it is not commercially manufactured, and in reality, a method of highly filling the above-mentioned ferrite or soft magnetic alloy powder is used.
Japanese Patent Laid-Open No. 2005-281783 JP-A-2005-251918

  This invention solves the said subject, and provides the noise suppression resin composite material with few thickness dependences of the noise suppression effect lightweight. According to the present invention, since it is not necessary to deposit a resin sheet with a magnetic metal or the like, it is possible to apply a noise suppression resin composite material to a noise generation source.

As a result of intensive studies, the present inventors have found that a noise suppression resin composite material including a resin, an insulated ultrafine powder, and a conductive filler exhibits a high noise suppression effect. That is, the present invention is as follows.
1. The noise suppression resin composite material containing following (a)-(c).
(A) Resin (b) Insulated ultrafine powder comprising a conductive ultrafine powder provided with an insulating film (c) Conductive filler The conductive ultrafine powder is made of a spherical carbon material having a particle diameter of 1 nm or more and 500 nm or less, a fibrous carbon material having a cross-sectional diameter of 1 nm or more and 500 nm or less, or a plate-like carbon material having a thickness of 1 nm or more and 500 nm or less, and the insulating film is a thermoplastic resin. Or made of a thermosetting resin, when the thickness of the insulating film is 0.3 nm or more, and when the conductive ultrafine powder is spherical, the particle diameter or less, and when fibrous, the cross-sectional diameter or less, In the case of a plate shape, the noise-suppressing resin composite material according to item 1, which is equal to or less than the thickness thereof.
3. The ratio of the total blended amount of the insulated ultrafine powder and the conductive filler and the blended amount of the resin is 50/50 to 5 in a volume ratio ((insulated ultrafine powder + conductive filler) / resin). The noise suppressing resin composite material according to Item 1, which is in the range of / 95.
4). The ratio of the blended amount of the insulated ultrafine powder and the blended amount of the conductive filler is 95/5 to 5/95 in volume ratio (insulated ultrafine powder / conductive filler). The noise suppression resin composite material according to Item 3.
5. The noise suppressing resin composite material according to claim 1, wherein the conductive filler is a conductive powder made of a carbon material.
6). The noise-suppressing resin composite material according to item 1, wherein the specific gravity is less than 2.
7). An electronic device using the noise-suppressing resin composite material described in Item 1 inside a housing.

  The noise-suppressing resin composite material of the present invention exhibits noise suppressing ability while maintaining the original excellent moldability, workability and lightness of the resin material. The noise-suppressing resin composite material of the present invention is useful for reducing the thickness of a noise-suppressing body that prevents radio wave interference inside a high-frequency electronic device by utilizing a wavelength shortening effect due to a high dielectric constant. Furthermore, it is also useful for suppressing unwanted noise in the microwave region.

  The insulated ultrafine powder used in the present invention is obtained by providing an electrically conductive ultrafine powder with an insulating film. When the conductive ultrafine powder is added alone to the resin material, it has an effect of reducing the volume resistance of the resin composite material, that is, imparting conductivity. In the present invention, conductive carbon materials such as natural graphite, artificial graphite, furnace carbon black, graphitized carbon black, carbon nanotube, and carbon nanofiber are used as the material constituting such a conductive ultrafine powder. These carbon materials are used not only as the core of the insulated ultrafine powder of the present invention but also as a conductive filler used in the noise suppressing resin composite material.

  The conductive ultrafine powder made of a carbon material is preferably subjected to an oxidation treatment on the surface in advance in order to apply a thermosetting or thermosetting resin film as described below, if necessary. As oxidation treatment, oxidation treatment in an oxygen-containing atmosphere, oxidation treatment with an aqueous solution of nitric acid, potassium permanganate, hydrogen peroxide, etc., oxidation treatment using an oxidation catalyst composed of ruthenium trichloride and sodium hypochlorite, etc. Is mentioned.

  Examples of the conductive ultrafine powder used in the present invention include spherical carbon materials having a particle diameter of 1 nm to 500 nm, preferably 5 nm to 300 nm, more preferably 10 nm to 100 nm. Such a spherical carbon material, for example, carbon black is obtained by thermally decomposing a hydrocarbon raw material in a gas phase. Graphitized carbon black vaporizes a carbon material by arc discharge and cools and solidifies the vaporized carbon vapor in a decompression vessel maintained at an internal pressure of 2 to 19 Torr by an atmosphere system of He, CO, or a mixed gas thereof. Can be obtained. Specifically, Seast S or Toka Black (# 7100F) manufactured by Tokai Carbon Co., Ltd., conductive carbon black # 5500, # 4500, # 4400, # 4300 or graphitized carbon black # 3855, # 3845, # 3800 Alternatively, examples include # 3050B, # 3030B, # 3230B, # 3350B, MA7, MA8, MA11 manufactured by Mitsubishi Chemical Corporation, or Ketjen Black EC, Ketjen Black EC600JD manufactured by Lion Corporation. Here, the spherical shape does not necessarily need to be a strict spherical shape, and may be an isotropic shape. For example, it may be a polyhedron with corners.

  The conductive ultrafine powder used in the present invention includes a fibrous carbon material having a cross-sectional diameter of 1 nm to 500 nm, preferably 5 nm to 300 nm, more preferably 10 nm to 200 nm. The length is preferably 3 to 300 times the cross-sectional diameter. Such fibrous carbon materials such as carbon nanofibers and carbon nanotubes can be obtained by mixing cobalt and iron organometallic compounds as a catalyst and a hydrocarbon raw material in a gas phase and heating. Some carbon nanofibers are obtained by melt spinning a phenolic resin and heating in a non-active atmosphere. Specific examples include VGCF and VGNF manufactured by Showa Denko KK, Carbale manufactured by GSI Creos Co., Ltd., and carbon nanofiber manufactured by Gunei Chemical Industry Co., Ltd. Here, the fiber shape means a shape extending in one direction, and may be, for example, a square shape, a round bar shape, or an oblong shape.

  Furthermore, the conductive ultrafine powder used in the present invention includes a plate-like carbon material having a thickness of 1 nm to 500 nm, desirably 5 nm to 300 nm, more desirably 10 nm to 200 nm. The length and width are preferably not less than 3 times and not more than 300 times the thickness. Such a plate-like carbon material can be obtained, for example, by refining, pulverizing, and classifying natural graphite or artificial graphite. Examples thereof include SNE series and SNO series manufactured by ESC Corporation, graphite made in Japan, scale-like graphite powder, exfoliated graphite powder, and the like. These may be further pulverized and precision classified. In addition, plate shape means the shape which one direction shrunk here, for example, a flat spherical shape and a scale shape may be sufficient.

  Next, the insulating film used in the present invention is one of the purposes for ensuring the overall insulation of the resin composite material. The thickness of the insulating coating is less than the particle diameter when the conductive ultrafine powder to be coated is spherical, less than the cross-sectional diameter when it is fibrous, and less than the thickness when it is plate-like. More preferably, the thickness of the insulating film is 0.3 nm or more, and the ratio of the particle diameter, the cross-sectional diameter, or the thickness of the conductive ultrafine powder to be coated is 0.01 or more and 0.9 or less. Most desirably, the thickness of the insulating film is 0.3 nm or more, and the ratio of the particle diameter, the cross-sectional diameter, or the thickness of the conductive ultrafine powder to be coated is 0.01 or more and 0.5 or less. If it is thinner than the above range, the insulating effect is reduced, and conduction may not be prevented and the dielectric may not function.

  The material of the insulating film in the present invention is a thermoplastic resin or a thermosetting resin. Thermoplastic resins include polyethylene, polyvinyl chloride, polypropylene, polystyrene, polyvinyl acetate, ABS resin, AS resin, acrylic resin, and other general-purpose plastics, polyacetal, polyimide, polycarbonate, modified polyphenylene ether (PPE), polybutylene terephthalate, etc. Engineering plastics, polyarylate, polysulfone, polyphenylene sulfide, polyetheretherketone, polyimide resin, fluororesin, polyamideimide, polyetheretherketone, and the like.

  Thermosetting resins include phenolic resin, amino resin (urea resin, melamine resin, benzoguanamine resin), unsaturated polyester resin, diallyl phthalate resin (allyl resin), alkyd resin, epoxy resin, urethane resin (polyurethane), silicon resin (Silicone).

  A known method can be used to form the insulating film. For example, by dropping a mixed solution in which a conductive ultrafine powder is dispersed and a thermoplastic resin is dissolved into a poor solvent, the resin is precipitated using the conductive ultrafine powder as a core, and is filtered and dried to conduct the conductive. A state in which a thermoplastic resin is adhered to the surface of the conductive ultrafine powder can be formed. Alternatively, a state in which the thermosetting resin is attached to the surface of the conductive ultrafine powder can be formed by grinding the mixture of the conductive ultrafine powder and the thermosetting resin monomer after thermosetting. Moreover, the state which the thermosetting resin adhered to the surface of electroconductive ultrafine powder can also be formed by disperse | distributing electroconductive ultrafine powder and a thermosetting resin monomer in a solvent, and spraying in the heated inert gas.

  As matrix resin components to which the insulated ultrafine powder obtained as described above is added, general-purpose plastics such as polyethylene, polyvinyl chloride, polypropylene, polystyrene, polyvinyl acetate, ABS resin, AS resin, acrylic resin, polyacetal, Super plastics such as polyimide, polycarbonate, modified polyphenylene ether (PPE), engineering plastics such as polybutylene terephthalate, polyarylate, polysulfone, polyphenylene sulfide, polyetheretherketone, polyimide resin, fluororesin, polyamideimide, polyetheretherketone Engineering plastics. A resin that can be processed at a temperature lower than the heat resistant temperature of the resin used for insulation is preferable.

  The resin component when blended with the insulated ultrafine powder is not only in the form of a polymer but also in the form of a polymerizable compound, that is, phenol resin, amino resin (urea resin, melamine resin, benzoguanamine resin), As a polymerizable compound such as a monomer or oligomer of thermosetting resin such as saturated polyester resin, diallyl phthalate resin (allyl resin), alkyd resin, epoxy resin, urethane resin (polyurethane), silicon resin (silicone) It may be polymerized later. A resin composition containing a urethane resin (polyurethane) is particularly desirable. This is because it is very flexible and difficult to break.

  The noise suppressing resin composite material of the present invention can be used by further adding a second filler, if necessary, for purposes other than noise suppression. As the second filler, glass fiber for improving elastic modulus, calcium carbonate for reducing molding shrinkage, talc used for improving surface smoothness and wear resistance, and for improving dimensional stability The mica used is mentioned. In addition, examples of fillers that impart flame retardancy, that is, flame retardants, include halogen-based or phosphorus-based flame retardants, aluminum hydroxide, and magnesium hydroxide. In addition, ferrite powder used in the prior art to adjust noise suppression characteristics, magnetic metal powder based on iron, tin oxide conductive powder, and conductive powder that also has an effect as a flame retardant Graphite powder or the like can be further added as a filler.

  In the present invention, the ratio of the total blending amount of the insulated ultrafine powder and the conductive filler and the resin blending amount is 50/50 in volume ratio ((insulated ultrafine powder + conductive filler) / resin). It is in the range of ~ 5/95. If there is more resin than this range, sufficient noise suppression effect cannot be obtained. On the other hand, if it is less than this, the inherent processability of the resin will be impaired. The range of 45/55 to 15/85 is desirable, and the range of 40/60 to 30/70 is particularly desirable.

  In the present invention, the ratio between the blended amount of the insulated ultrafine powder and the blended amount of the conductive filler is in the range of 95/5 to 5/95 by volume ratio (insulated ultrafine powder / conductive filler). is there. Even if there are more or less conductive fillers than this range, a noise suppression effect cannot be obtained in a high frequency range of 100 MHz or higher. Desirably, depending on the volume ratio of the total blending amount of the insulated ultrafine powder and the conductive filler and the blending amount of the resin, it is preferably in the range of 80/20 to 20/80, particularly preferably 50/50 to 80. The range is / 20.

  Since the noise suppressing resin composite material of the present invention uses a carbon material as a raw material for the insulated ultrafine powder, its specific gravity can be reduced to 2 or less.

  The noise suppression resin composite material of the present invention relates to EMI and immunity in which electromagnetic waves are unintentionally radiated and transmitted from a communication device or various electronic devices, or the device itself malfunctions due to external and internal interference. Useful for solving problems. Noise suppression resin composite material in the form of a sheet or film on parts inside the casing of electronic equipment, for example, flexible printed circuit board cables that connect display signal processing circuits to display devices such as LSIs and liquid crystal displays that process data signals An unnecessary electromagnetic wave can be suppressed by sticking or apply | coating. Moreover, an unnecessary electromagnetic wave can be suppressed also by affixing and apply | coating a noise suppression resin composite material to the housing inner surface.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these Examples.

Regarding the noise suppression effect, according to the IEC standard (No .: IEC62333-1, IEC62333-2), a sheet made of a noise suppression resin composite material is placed on the microstrip line shown in FIG. 8722 ES), and the noise suppression effect was measured.
The specific gravity was measured by molding the noise-suppressing resin composite material into a disc of 30 mmφ and 3 mm thickness, measuring this weight, and placing it in a graduated cylinder filled with water and measuring the volume.

Preparation example 1 of insulated ultrafine powder
1 kg of carbon black (spherical with a particle diameter of 30 to 50 nm and an average diameter of 40 nm) was put into 10 L of N, N-dimethylacetamide (DMAc) and stirred to prepare a dispersion. Further, 1 kg of polyamideimide (PAI) was dissolved to prepare a mixed solution containing carbon black / PAI = 50/50 wt%. The obtained mixed solution was dropped into 20 L of stirred methanol. Next, the solid was separated by suction filtration. The cake in which DMAc was sufficiently washed with methanol was dried to obtain carbon black particles coated with PAI. As a result of observation with a transmission electron microscope (SEM), the PAI layer coated on the surface of the carbon black particles was about 30 nm in thickness.

Preparation example 2 of insulated ultrafine powder
In the same manner as in the method for synthesizing ultrafine powder 1, except that natural graphite (thickness 100 to 200 nm, average thickness 150 nm, 1 to 3 μm square, average 2 μm square plate shape) was used instead of carbon black, PAI Coated graphite particles were obtained. As a result of observation with a transmission electron microscope (SEM), the PAI layer coated on the surface of the graphite particles was about 45 nm in thickness.

Preparation example 3 of insulated ultrafine powder
1 kg of carbon black (spherical with a particle diameter of 30 to 50 nm and an average diameter of 40 nm) was put into 10 L of methyl ethyl ketone (MEK), and mixed by stirring to obtain a dispersion. Further, 1 kg of bisphenol A type epoxy monomer and an imidazole effect catalyst were dissolved to prepare a mixed solution containing carbon black / epoxy monomer = 50/50 wt%. MEK was distilled under reduced pressure, and the resulting paste was heated at 120 ° C. for 1 hour to obtain carbon black particles coated with an epoxy resin. As a result of observation with a transmission electron microscope (SEM), the thickness of the epoxy resin layer coated on the surface of the carbon black particles was about 35 nm.

Preparation example 4 of insulated ultrafine powder
The carbon nanofiber particles coated with an epoxy resin were similarly prepared except that carbon nanofibers (fiber shape having a cross-sectional diameter of 150 nm and a length of 5 to 6 μm) were used instead of carbon black in the insulating ultrafine powder synthesis method 3. Obtained. As a result of observation with a transmission electron microscope (SEM), the epoxy resin layer coated on the surface of the carbon nanofiber particles had a thickness of about 40 nm.

Example 1
The insulated ultrafine powder obtained in Preparation Example 1 above and carbon black (spherical with a particle diameter of 60 to 80 nm and an average diameter of 66 nm) have a volume ratio (insulated ultrafine powder / carbon black) of 80/20. Mixed. This mixed powder and polypropylene elastomer were melt-kneaded at a volume ratio (mixed powder / polypropylene) 50/50. A sheet having a thickness of 100 μm was prepared by hot melt pressing.
This sheet was placed on the microstrip line shown in FIG. 1 in accordance with IEC standards (No .: IEC 62333-1, IEC 62333-2), and the noise suppression effect was measured. At 1 GHz, the noise absorption rate was 78%. The specific gravity was 1.3.

Example 2
A sheet having a thickness of 100 μm was produced in the same manner as in Example 1 except that the mixed powder / polypropylene volume ratio was 70/30. At 1 GHz, the noise absorption rate was 26%. The specific gravity was 1.2.

Example 3
In Example 1, a sheet having a thickness of 100 μm was prepared in the same manner except that the insulated ultrafine powder obtained in Preparation Example 2 was used instead of the insulated ultrafine powder obtained in Preparation Example 1. At 1 GHz, the noise absorption rate was 67%. The specific gravity was 1.3.

Example 4
The insulated ultrafine powder produced in Preparation Example 3 and carbon black (spherical with a particle diameter of 60 to 80 nm and an average diameter of 66 nm) are set so that the volume ratio (insulated ultrafine powder / carbon black) is 80/20. Mixed. The mixed powder and flexible epoxy monomer were prepared so that the volume ratio (mixed powder / epoxy) was 50/50, and an imidazole-based curing catalyst was added to prepare a paste. The obtained paste was applied to a PET film using a doctor blade and then heated at 120 ° C. for 1 hour to produce a 100 μm thick sheet. At 1 GHz, the noise absorption rate was 58%. The specific gravity was 1.5.

Example 5
In Example 4, instead of the insulated ultrafine powder obtained in Preparation Example 3, a sheet having a thickness of 100 μm was produced in the same manner except that the insulated ultrafine powder obtained in Preparation Example 4 was used. At 1 GHz, the noise absorption rate was 71%. The specific gravity was 1.5.

Comparative Example 1
Carbon black (spherical with a particle diameter of 60 to 80 nm and an average diameter of 66 nm) and polypropylene elastomer were melt-kneaded at a volume ratio (mixed powder / polypropylene) 50/50. A sheet having a thickness of 100 μm was prepared by hot melt pressing.
At 1 GHz, the noise absorption rate was 4%. The specific gravity was 1.2.

Comparative Example 2
The insulated ultrafine powder obtained in Preparation Example 1 and polypropylene elastomer were melt-kneaded at a volume ratio (mixed powder / polypropylene) 50/50. A sheet having a thickness of 100 μm was prepared by hot melt pressing.
The noise suppressing effect of this sheet was 3%. The specific gravity was 1.3.

Schematic diagram of the equipment used to measure the noise suppression effect

Explanation of symbols

1 Microstripline signal line 2 Microstripline polytetrafluoroethylene insulation layer 3 Macrostripline ground plane 4 50Ω coaxial cable 5 Network analyzer

Claims (7)

Noise suppression resin composite material including the following (a) to (c),
(A) resin,
(B) Insulated ultrafine powder obtained by providing an insulating coating on conductive ultrafine powder,
(C) Conductive filler.   The conductive ultrafine powder is made of a spherical carbon material having a particle diameter of 1 nm or more and 500 nm or less, a fibrous carbon material having a cross-sectional diameter of 1 nm or more and 500 nm or less, or a plate-like carbon material having a thickness of 1 nm or more and 500 nm or less, and the insulating film is a thermoplastic resin. Or made of a thermosetting resin, when the thickness of the insulating film is 0.3 nm or more, and when the conductive ultrafine powder is spherical, the particle diameter or less, and when fibrous, the cross-sectional diameter or less, The noise suppressing resin composite material according to claim 1, wherein in the case of a plate shape, the thickness is not more than the thickness.   The ratio of the total blending amount of the insulated ultrafine powder and the conductive filler and the blended amount of the resin is 50/50 to 5 in volume ratio ((insulated ultrafine powder + conductive filler) / resin). The noise suppressing resin composite material according to claim 1, which is in the range of / 95.   The ratio between the blended amount of the insulated ultrafine powder and the blended amount of the conductive filler is in the range of 95/5 to 5/95 in volume ratio (insulated ultrafine powder / conductive filler). Item 4. A noise suppressing resin composite material according to Item 3.   The noise suppressing resin composite material according to claim 1, wherein the conductive filler is a conductive powder made of a carbon material. The noise suppressing resin composite material according to claim 1, wherein the specific gravity is less than 2.   The electronic device which used the noise suppression resin composite material of Claim 1 for the inside of a housing | casing.

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