JP2009016506A - Noise suppressor using dielectric characteristic - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lightweight noise suppressor small in thickness dependency of a noise suppression effect. <P>SOLUTION: In the noise suppressor, a reflection coefficient at a frequency not higher than 1 GHz, a reflection coefficient S11 at a frequency of 1-3 GHz, and a transmission coefficient S21 at 1 GHz measured by IEC standards (Nos. IEC62333-1 and IEC62333-2) are not larger than -5 dB, not larger than -10 dB, and not larger than -2 dB, respectively. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a noise suppressor or electromagnetic interference suppressor that is mounted or applied to prevent unwanted electromagnetic waves generated in electronic equipment from leaking to the outside, interference between internal circuits, and malfunctions caused by external electromagnetic waves. .

  Problems related to EMI and immunity that cause electromagnetic waves to be radiated and transmitted to the outside unintentionally from communication devices and various electronic devices, and cause malfunctions of the device 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). However, as the radio wave used becomes higher 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 of a very heavy soft magnetic alloy having a specific gravity of about 10 is highly filled, the specific gravity of the resin composite material increases to 3 or more, and there is a problem that it is not particularly suitable for weight reduction of portable communication devices. Moreover, the thickness dependency of the noise suppression effect is strong. In particular, when the thickness of the noise suppression body is 300 μm or less, there arises a problem that the noise suppression effect is lowered.

Moreover, although the noise suppression body as a composite_body | complex which vapor-deposited the magnetic metal on the surface of the resin sheet which added the conductive filler and the dielectric filler was also proposed (for example, refer patent document 2), noise suppression is proposed in this case 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 body with few thickness dependences of the noise suppression effect lightweight. According to the present invention, since it is not necessary to deposit the resin sheet with a magnetic metal or the like, it is possible to apply the noise suppressor as a paint to a noise generation source.

As a result of intensive studies, the present inventors have found that by using dielectric characteristics, a lighter, thinner, and higher noise suppression effect is exhibited than a noise suppression body using a conventional magnetic body. That is, the present invention is as follows.
(1) The reflection coefficient S11 at 1 GHz or less measured by the IEC standard (No .: IEC62333-1, IEC62333-2) is −5 dB or less, the reflection coefficient from 1 GHz to 3 GHz is −10 dB or less, and the transmission coefficient S21 at 1 GHz is -2 dB or less noise suppressor (2) Noise suppressor using dielectric characteristics, thickness t (mm), complex relative permittivity real part εr ', complex relative permittivity imaginary part εr " The noise suppressor according to (1), which satisfies the formula:
εr '・ t ≦ 300 (mm)
εr '' ・ t ≧ 3 (mm)
(3) The noise suppressor according to (1), comprising a resin composite material having a relative dielectric constant of 10 or more.
(4) The noise suppressor according to (1), comprising a resin composite material having a specific gravity of less than 3.
(5) The noise suppressor according to (1) to (4), wherein the resin contains a dielectric filler having a relative dielectric constant of 100 or more.
(6) The dielectric filler is made of a metal oxide powder represented by a composition formula MTi _1-x Zr _x O 3 (M is a divalent metal element, x is 0 or more and less than 1) (5 ) The noise suppressor described.
(7) Any of (5) and (6) obtained by blending the dielectric filler and the resin in a volume ratio (insulated ultrafine powder / resin) in the range of 5/95 to 50/50. Noise suppression body.
(8) Insulating metal oxide or a spherical conductive material having a particle diameter of 1 nm to 500 nm, a fibrous shape having a cross-sectional diameter of 1 nm to 500 nm, or a plate-shaped conductive ultrafine powder having a thickness of 1 nm to 500 nm. The noise suppressor according to (1), comprising an insulated ultrafine powder and a resin provided with an insulating film composed of the hydrate.
(9) The noise suppressor according to (7), wherein the conductive ultrafine powder is a conductive carbon material.
(10) When the thickness of the insulating film is 0.3 nm or more and the conductive ultrafine powder as the core is spherical, the particle diameter is smaller than the particle diameter. In some cases, the noise suppressor according to (7) or (8), wherein an insulating ultrafine powder having a thickness equal to or less than the thickness is used.
(11) In any one of (7) to (9) obtained by blending the insulated ultrafine powder and the resin in a volume ratio (insulated ultrafine powder / resin) in the range of 5/95 to 50/50. The noise suppressor described.
(12) The noise suppressor according to any one of (1) to (10), which contains a filler.
(13) The noise suppressor according to (11), wherein the filler is a conductive filler.
(14) It is obtained by blending the total of the dielectric filler and the conductive filler and the resin in a volume ratio (dielectric filler + conductive filler / resin) range of 90/10 to 0/60. The noise suppressor according to (12), comprising a resin composite material to be used.
(15) A resin composite material obtained by blending the dielectric filler and the conductive filler in a volume ratio (dielectric filler / conductive filler) 90/10 to 10/90 range is used (12 ) The noise suppressor described.
(16) The noise suppressor according to (12), wherein the conductive filler is made of conductive powder made of a carbon material.
(17) Electronic equipment (18) using a casing made of a noise suppressor according to (1) to (16) (18) Noise suppression film (19) (1) comprising a noise suppressor according to (1) to (16) Electronic equipment using the noise suppression body according to (16) or the noise suppression film according to (18) inside the casing.
(20) A digital camera using the noise suppression body according to (1) to (16) or the noise suppression film according to (18) inside a housing.
(21) A mobile phone using the noise suppression body according to (1) to (19) or the noise suppression film according to (18) inside a casing.

  According to the present invention, not only the noise can be suppressed, but also the adverse effect on the noise generation source can be reduced.

The evaluation method for the noise suppression effect is defined by the IEC standard (No .: IEC62333-1, IEC62333-2).
A film or sheet-like noise suppressor is placed on the microstrip line 1 connected to the network analyzer 5 shown in FIG. 1, and the signal transmitted from the port 1 (FIG. 1-6) of the network analyzer 5 becomes the noise suppressor. The power of the signal reaching the port 2 (FIG. 1-7) and the power of the signal reflected on the port 1 itself are measured via the mounted microstrip line.
The smaller the power ratio T of the reaching signal from the port 1 (FIG. 1-6) to the port 2 (FIG. 1-7), the greater the noise suppression effect. Usually, the following amounts are used.
Transmission coefficient: S21 (dB) = 10 · log (T)
Further, the smaller the power ratio R of the reflected signal in the microstrip line, the smaller the influence of the noise suppressor on the transmission source circuit. Usually, the following amounts are used.
Reflection coefficient: S11 (dB) = 10 · log (R)

The noise suppression body needs not only to have a large noise suppression effect but also to have a small influence on the transmission source circuit. Therefore, in the measurement method specified in the IEC standard, it is desirable that S11 is −5 (dB) or less and S21 is −1 (dB) or less. Desirably, the reflection coefficient S11 at 1 GHz or less is −10 dB or less, the reflection coefficient S11 from 1 GHz to 3 GHz is −15 (dB) or less, and the transmission coefficient S21 at 1 GHz is −2 (dB) or less. The most desirable is a noise suppressor that satisfies the above conditions and has a reflection coefficient S11 from 1 GHz to 3 GHz of −20 (dB) or less.
When the transmission coefficient is larger than the above range, the noise suppression effect is reduced. If the reflection coefficient is larger than the above range, the circuit operation itself is not normal.

When the thickness of the noise suppressor is t (mm) and the real part εr ′ of the complex relative dielectric constant, εr ′ · t needs to be 300 mm or less. It is desirably 100 mm or less, and more desirably 30 mm or less. If it is larger than this, it adversely affects the operation of the circuit itself that is the source of unwanted radiation.
In addition, the product of the thickness t (mm) of the noise suppression body and the imaginary part εr ″ of the complex relative dielectric constant needs to be larger than 3 mm. It is desirably 6 mm or more, and more desirably 10 mm or more. If it is smaller than this, unnecessary radiation and internal interference between circuits cannot be effectively suppressed.
In the present invention, a noise suppression body having a thickness of 0.3 mm or less is referred to as a noise suppression film.

According to the present invention, the thickness t (mm), the real part εr ′ of the complex relative permittivity, the imaginary part εr ″ of the complex relative permittivity satisfy the following conditions, and by applying or applying a noise suppressor, Unwanted radiation from the device to the outside and interference between circuits inside can be effectively suppressed.
εr '・ t ≦ 300 (mm)
εr '' ・ t ≧ 3 (mm)
The relative dielectric constant is a quantity indicating how easily a certain substance is charged compared to a vacuum (εr ′ = 1, εr ″ = 0). The complex relative permittivity is a relative permittivity represented by a complex number in which the amount of charge actually stored by charging corresponds to the real part and the amount of charge lost as current corresponds to the imaginary part.

  Unlike the prior art, the noise suppressor of the present invention does not use a magnetic metal having a large specific gravity, so that the specific gravity can be reduced to 3 or less. This contributes to weight reduction of an electronic device using this noise suppression body.

The dielectric filler used in the present invention is a filler having an effect of increasing the dielectric constant when added alone to a resin, and is composed of a metal oxide. A metal oxide desirable as a dielectric filler used in the present invention includes a metal oxide having a dielectric constant of 100 or more. Specific examples include rutile titanium dioxide (TiO ₂ ) and barium titanate (BaTiO ₃ ). Especially desirable are compositional formula _{MTi 1-x Zr x O 3} (M is a divalent metal element, x is 0 to less than 1) is a metal oxide represented by, in particular barium titanate (BaTiO ₃₎ , Strontium titanate (SrTiO ₃ ), lead titanate (PbTiO ₃ ), barium zirconate titanate (BaTi _0.5 Zr _0.5 O ₃ ), lead zirconate titanate (PbTi _0.5 Zr _0.5 O) ₃ ).

The conductive filler used in the present invention is a filler having an effect of imparting conductivity when added to a resin. Examples of such fillers include powders made of any of metals, conductive metal oxides, and carbon materials. As the metal powder, any of metals that do not exhibit magnetism such as copper and aluminum and metals that exhibit magnetism such as iron can be used in the present invention.
Examples of the conductive metal oxide include so-called ATO, that is, tin dioxide (SnO ₂ ) doped with antimony (Sb), so-called ITO, that is, tin (Sn) -doped indium trioxide (In ₂ O ₃ ), and aluminum (Al). Zinc oxide doped with (ZnO).

  Among the conductive fillers, a conductive powder made of a carbon material, that is, a conductive carbon material fine powder is particularly desirable. Specifically, conductive carbon materials such as natural graphite, artificial graphite, furnace carbon black, graphitized carbon black, carbon nanotube, and carbon nanofiber are used. The carbon material has a small specific gravity of 2.2, has a feature not found in other conductive materials, and has an effect of reducing the weight of the noise suppressor.

  In the present invention, the volume ratio (dielectric filler + conductive filler / resin) between the total of the dielectric filler and the conductive filler and the resin is 90/10 to 40/60. If the resin content is greater than this range, a sufficient noise suppression effect cannot be obtained. On the other hand, if it is less than this, the original processability of the resin composition will be impaired.

  In the present invention, the volume ratio of the dielectric filler to the conductive filler (dielectric filler / conductive filler) is 90/10 to 10/90. A desirable range is 80/20 to 20/80 although it depends on the volume ratio of the total of the dielectric filler and the conductive filler and the resin. 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.

  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 a noise suppressor.

  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, Seest S and Toka Black (# 7100F) manufactured by Tokai Carbon Co., Ltd., conductive carbon black # 5500, # 4500, # 4400, # 4300 and 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, polyether ether ketone, polyimide resin, fluororesin, polyamide imide, polyether ether ketone, 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 nucleus, 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 adhered to the surface of the conductive ultrafine powder can be formed by pulverizing 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.

  The conductive carbon material fine powder used in the present invention includes a spherical carbon material having a particle diameter of 1 nm to 12 μm, preferably 5 nm to 3 μm, more preferably 10 nm to 1 μm. 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, Toast Carbon Co., Ltd. Seast S, conductive carbon black # 5500, # 4500, # 4400, # 4300, graphitized carbon black # 3855, # 3845, # 3800, or Mitsubishi Chemical Corporation ) # 3050B, # 3030B, # 3230B, # 3350B, MA7, MA8, MA11, 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 carbon material fine powder used in the present invention includes a fibrous carbon material having a cross-sectional diameter of 1 nm to 12 μm, desirably 5 nm to 3 μm, more desirably 10 nm to 1 μm. 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 carbon material fine powder used in the present invention includes a plate-like carbon material having a thickness of 1 nm to 12 μm, preferably 5 nm to 3 μm, more preferably 10 nm to 1 μm. 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.

  As the resin component used in the present invention, thermoplastic resins such as PVC resin, phenoxy resin, fluorocarbon resin, PPS resin, PPE resin, polystyrene resin, polyolefin resin, polyimide resin, polypropylene resin, polyethylene resin, polyamide resin, Alternatively, these mixed resins can be mentioned.

  In addition, 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, an acrylic resin, a phenoxy resin, an epoxy resin, a cyanate ester resin, a vinyl ester resin, It may be blended as a polymerizable compound such as a monomer or oligomer of a thermosetting resin such as a phenol resin, a xylene resin, a melamine resin, or a polyurethane resin and polymerized later.

  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 for adjustment of noise suppression characteristics, magnetic metal powder based on iron, expanded graphite powder that is conductive powder that also has an effect as a flame retardant, etc. as a filler, Further, it can be added.

  The noise suppressor of the present invention is radiated and transmitted to the outside unintentionally from various electronic devices such as communication devices such as mobile phones, smartphones, digital TV transceivers, digital cameras and PDAs, and external and internal It is useful for solving problems related to EMI and immunity that cause malfunctions of the equipment itself due to interference.

The noise suppressor of the present invention is formed into a sheet, particularly a film having a thickness of 300 μm or less, or a film coated with a film-like substrate such as polyethylene terephthalate or polyimide. By adhering or applying to parts such as 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, unwanted electromagnetic waves can be suppressed. .
Moreover, unnecessary electromagnetic waves can also be suppressed by forming the casing itself with a noise suppressing body, or attaching or applying a noise suppressing resin composite material to the inner surface of the casing.

  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 body is placed on the microstrip line shown in FIG. The reflection coefficient S11 and the transmission coefficient S21 were measured by 8722ES).
The specific gravity was measured by molding a resin composite material into a disk having a diameter of 30 mmφ and a thickness of 3 mm, measuring the weight, and placing the resin composite in a measuring cylinder with water, and measuring the volume.

Example 1
When potassium tetratitanate fiber (average fiber length 16 μm) was pulverized in polyethylene glycol for 10 minutes with a ball mill type continuous pulverizer, this was stirred in a 1 N / liter nitric acid aqueous solution for 2 hours and then thoroughly washed with water. After drying, classification was performed to obtain a titania fibrous material. 10 g of this fibrous material was dispersed in 260 ml of a 10% aqueous solution of barium acetate, and further 70 g of a 20% aqueous solution of ammonium carbonate was added dropwise over about 1 hour with stirring to react. After dehydration filtration, it was washed with water and dried. Further, 10 g of this product was placed in an alumina crucible and heated in an electric furnace at 970 ° C. for 2 hours in an oxidizing atmosphere. As a result of X-ray diffraction of this after air cooling, only the peak of barium titanate was detected. As a result of observation with an electron microscope, it was a fibrous material having an average fiber length of 1.5 μm, an average fiber diameter of 0.4 μm, and an average aspect ratio of 3.7.
The fibrous barium titanate powder thus produced and carbon black (spherical with a particle diameter of 60 to 80 nm and an average diameter of 66 nm) are adjusted so that the volume ratio (fibrous barium titanate / carbon black) is 80/20. Mixed. This mixed powder and polyphen sulfide were melt-kneaded at a volume ratio (mixed powder / polyphen sulfide) of 55/45. A sheet having a thickness of 158 μm was prepared by hot pressing.
This sheet was placed on the microstrip line shown in FIG. 1 according to IEC standards (No .: IEC62333-1, IEC62333-2), and the reflection coefficient S11 and the transmission coefficient S21 were measured. At 1 GHz, the transmission coefficient S21 was −2 (dB), and the reflection coefficient S11 was −15 dB at 1 GHz to 3 GHz, and −16 dB at 1 GHz to 3 GHz. The real part of the complex relative dielectric constant was 76 and the imaginary part was 89. Therefore, εr ′ · t = 12, εr ″ · t = 14. The specific gravity was 2.9.

Example 2
Example 1 was repeated except that calcium acetate was used in place of barium acetate and a liquid crystal polymer was used in place of polyphenylene sulfide. Further, the reflection coefficient S11 and the transmission coefficient S21 were measured in the same manner as in Example 1. At 1 GHz, the transmission coefficient S21 was −2 (dB), and the reflection coefficient S11 was −15 (dB) or less in a band of 1 GHz or less, and −16 (dB) or less from 1 GHz to 3 GHz. The real part of the complex dielectric constant was 69, and the imaginary part was 82. Therefore, εr ′ · t = 11 and εr ″ · t = 13. The specific gravity was 2.6.

Example 3
Volume ratio (strontium titanate powder / natural graphite) of strontium titanate powder (10 μmφ) and natural graphite (thickness 100-200 nm, average thickness 150 nm, 1-3 μm square, average 2 μm square plate) is 50/50 It mixed so that it might become. This mixed powder and syndiotactic polystyrene were melt-kneaded at a volume ratio (mixed powder / syndiotactic polystyrene) of 75/25. A 120 μm thick sheet was prepared by hot pressing. The reflection coefficient S11 and the transmission coefficient S21 were measured in the same manner as in Example 1. At 1 GHz, the transmission coefficient S21 was −2 (dB), and the reflection coefficient S11 was −15 (dB) and −16 (dB) at 1 GHz to 3 GHz in a band of 1 GHz or less. The real part of the complex dielectric constant was 42 and the imaginary part was 51. Therefore, εr ′ · t = 5.2 and εr ″ · t = 6.1. The specific gravity was 2.8.

Example 4
The mixed powder used in Example 3 and the bisphenol A type epoxy monomer to which an imidazole-based curing catalyst was added were dispersed and dissolved in methyl ethyl ketone at a volume ratio (mixed powder / epoxy monomer) of 65/35 to prepare a varnish. . The varnish was applied to the microstrip line shown in FIG. 1 using a doctor blade, and cured at 120 ° C. for 1 hour to form an 87 μm thick coating layer. The reflection coefficient S11 and the transmission coefficient S21 were measured in the same manner as in Example 1. At 1 GHz, the transmission coefficient S21 was −2 (dB), and the reflection coefficient S11 was −15 (dB) and −16 (dB) at 1 GHz to 3 GHz in a band of 1 GHz or less. Using a paste obtained by drying the varnish, a tablet with a diameter of 30 mmφ and a thickness of 3 mm was prepared, and the specific gravity was measured to be 2.5. The real part of the complex dielectric constant was 36, and the imaginary part was 48. Therefore, εr ′ · t = 3.1 and εr ″ · t = 4.2.

Comparative Example 1
An iron aluminum silicon (10 wt% Si-5.5 wt% Al-balance F e and inevitable impurities) alloy powder having an average particle diameter of 45 µm prepared by a water atomization method was prepared, and this powder was combined with n-hexane. After putting into a sand grind mill and grinding for 12 hours, oxidation treatment was performed, and annealing treatment was performed at 850 ° C. for 3 hours in an Ar gas atmosphere to obtain a flat powder. The flat powder and polyethylene chloride were dispersed and dissolved in toluene at a volume ratio of 50/50 to prepare a paste.
Using this paste, a film was formed by a doctor blade method, subjected to heat treatment, and then cured at 85 ° C. for 24 hours to prepare a sheet having a thickness of 300 μm.
The reflection coefficient S11 and the transmission coefficient S21 were measured in the same manner as in Example 1. At 1 GHz, the transmission coefficient S21 was −1.2 (dB), and the reflection coefficient S11 was −7 dB in a band of 1 GHz or less, and −5 dB at 1 GHz to 3 GHz. The specific gravity was 3.5.

Comparative Example 2
Example 1 was repeated except that carbon black was not used. At 1 GHz, the transmission coefficient S21 was -0.03 (dB). The real part 21 and the imaginary part 0.04 of the complex relative dielectric constant. Therefore, εr ′ · t = 3 and εr ″ · t = 6 × 10 ⁻³ .

Comparative Example 3
The procedure was the same as Example 1 except that fibrous barium titanate was not used. At 1 GHz, the transmission coefficient S21 was −9 (dB), but the reflection coefficient at 1 GHz was −4 dB. The real part 2835 and the imaginary part 3802 of the complex relative dielectric constant. Therefore, εr ′ · t = 448 and εr ″ · t = 601.

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 5
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.
The reflection coefficient S11 and the transmission coefficient S21 were measured in the same manner as in Example 1. At 1 GHz, the transmission coefficient S21 was −3 (dB), and the reflection coefficient S11 was −11 (dB) in a band of 1 GHz or less, and −14 (dB) at 1 GHz to 3 GHz. The specific gravity was 1.3. The real part of the complex relative dielectric constant was 540, and the imaginary part was 990. Therefore, εr ′ · t = 54 and εr ″ · t = 99.

Example 6
A sheet having a thickness of 100 μm was produced in the same manner as in Example 5 except that the mixed powder / polypropylene volume ratio was 70/30. At 1 GHz, the transmission coefficient S21 was −7 (dB), and the reflection coefficient S11 was −13 (dB) in the band below 1 GHz, and −21 (dB) at 1 GHz to 3 GHz. The specific gravity was 1.2. The real part of the complex dielectric constant was 21 and the imaginary part was 41. Therefore, εr ′ · t = 2 and εr ″ · t = 4.

Example 7
In Example 5, instead of the insulated ultrafine powder obtained in Preparation Example 1, a sheet having a thickness of 100 μm was produced in the same manner except that the insulated ultrafine powder obtained in Preparation Example 2 was used. At 1 GHz, the transmission coefficient S21 was −6 (dB), and the reflection coefficient S11 was −14 (dB) in the band below 1 GHz, and −18 (dB) from 1 GHz to 3 GHz. The specific gravity was 1.3. The real part of the complex relative dielectric constant was 490, and the imaginary part was 1010. Therefore, εr ′ · t = 49 and εr ″ · t = 101.

Example 8
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 transmission coefficient S21 was −7 (dB), and the reflection coefficient S11 was −12 (dB) in a band of 1 GHz or less, and −21 (dB) from 1 GHz to 3 GHz. The specific gravity was 1.5. The real part of the complex relative dielectric constant was 490, and the imaginary part was 1010. Therefore, εr ′ · t = 49 and εr ″ · t = 101.

Example 9
In Example 8, a sheet having a thickness of 100 μm was prepared in the same manner except that the insulated ultrafine powder obtained in Preparation Example 4 was used instead of the insulated ultrafine powder obtained in Preparation Example 3. At 1 GHz, the transmission coefficient S21 was −10 (dB), and the reflection coefficient S11 was −13 (dB) in a band of 1 GHz or less, and −19 (dB) at 1 GHz to 3 GHz. The specific gravity was 1.5. The real part of the complex relative dielectric constant was 190 and the imaginary part was 410. Therefore, εr ′ · t = 19 and εr ″ · t = 41.

Comparative Example 4
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.
As a result of measurement in the same manner as in Example 1, the transmission coefficient S21 was −9 (dB), but the reflection coefficient at 1 GHz was −4 (dB) and −6 (dB) at 1 GHz to 3 GHz. The specific gravity was 1.2. The real part of the complex relative dielectric constant was 3120, and the imaginary part was 4100. Therefore, εr ′ · t = 310 and εr ″ · t = 410.

Comparative Example 5
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.
As a result of measurement in the same manner as in Example 1, the transmission coefficient S21 was −0.1 (dB), and the reflection coefficient at 1 GHz was −3 (dB) and from 1 GHz to 3 GHz was −4 (dB). The specific gravity was 1.3. The real part 35 and the imaginary part of the complex relative dielectric constant were 0.7. Therefore, εr ′ · t = 310 and εr ″ · t = 0.07.

  From the series of Examples and Comparative Examples 3 and 5, it is effective to set εr ′ · t ≦ 300 so that the reflection coefficient corresponding to the influence of the noise suppressor on the circuit is −5 (dB) or less. I know that there is. Further, from the series of Examples and Comparative Examples 2 and 4, it can be seen that it is effective to set εr ″ · t ≧ 3 to increase the noise suppression effect and to reduce the transmission coefficient to −2 (dB) or less. .

  The noise suppressor created in the series of examples was attached in place of the noise suppressor attached to the digital camera unit of a commercially available mobile phone. The digital camera image flicker that occurred when shooting dark scenes was smaller than that of the conventional noise suppressor, but when using the noise suppressor created in the comparative example, it was already installed. Compared with the noise suppressor, the flickering of the image did not change. From this, it can be seen that the noise suppressor having a small reflection coefficient at 1 GHz or more is useful.

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 6 Network analyzer port 1
7 Network analyzer port 2

Claims (21)

  The reflection coefficient at 1 GHz or less measured by the IEC standard (No .: IEC62333-1, IEC62333-2) is -5 dB or less, the reflection coefficient S11 of 1 GHz to 3 GHz is -10 dB or less, and the transmission coefficient S21 at 1 GHz is -2 dB or less. Noise suppression body that is. The noise suppression body using dielectric characteristics, wherein the thickness t (mm), the real part εr ′ of the complex relative permittivity, and the imaginary part εr ″ of the complex relative permittivity satisfy the following expressions: body.
εr '・ t ≦ 300 (mm)
εr '' ・ t ≧ 3 (mm)   The noise suppression body according to claim 1, comprising a resin composite material having a real part εr ′ of a complex relative dielectric constant of 10 or more. The noise suppressor according to claim 1, comprising a resin composite material having a specific gravity of less than 3.   The noise suppression body according to claim 1, wherein the resin includes a dielectric filler having a relative dielectric constant real part εr ′ of 100 or more. Said dielectric filler composition formula _{MTi 1-x Zr x O 3} (M is a divalent metal element, x is 0 or more and less than 1) according to claim 4, wherein the formed of a metal oxide powder represented by Noise suppression body. The noise suppressor according to claim 4, which is obtained by blending a dielectric filler and a resin in a volume ratio (insulated ultrafine powder / resin) range of 5/95 to 50/50. Insulating metal oxide or hydration thereof into a spherical conductive powder having a particle diameter of 1 nm to 500 nm, a fibrous shape having a cross-sectional diameter of 1 nm to 500 nm, or a plate-like conductive ultrafine powder having a thickness of 1 nm to 500 nm. The noise suppression body according to claim 1, comprising an insulating ultrafine powder and a resin provided with an insulating film composed of a material.   The noise suppressor according to claim 7, wherein the conductive ultrafine powder is a conductive carbon material.   In the case where the thickness of the insulating film is 0.3 nm or more and the conductive ultrafine powder as a core is spherical, the particle diameter is smaller than that, the fibrous diameter is less than the sectional diameter, and the plate is The noise suppressor according to claim 7 or 8, wherein an insulating ultrafine powder having a thickness equal to or less than the thickness is used. The noise suppressor according to any one of claims 7 to 9, obtained by blending an insulated ultrafine powder and a resin in a volume ratio (insulated ultrafine powder / resin) in the range of 5/95 to 50/50. . The noise suppression body in any one of Claims 7-10 containing a filler.   The noise suppressor according to claim 11, wherein the filler is a conductive filler.   Resin to be used obtained by blending the total amount of the insulating ultrafine powder, the conductive filler and the resin in a volume ratio (dielectric filler + conductive filler / resin) in the range of 90/10 to 40/60. The noise suppressor according to claim 12, comprising a composite material.   13. The resin composite material obtained by blending the insulating ultrafine powder and the conductive filler in a volume ratio of 90/10 to 10/90 (insulated ultrafine powder / conductive filler). The noise suppressor described.   13. The noise suppressor according to claim 12, wherein the conductive filler is made of conductive powder made of a carbon material. Electronic equipment using a housing comprising the noise suppressor according to claim 1. The noise suppression film which consists of a noise suppression body of Claims 1-16   The electronic device which used the noise suppression body of Claims 1-16, or the noise suppression film of Claim 18 inside the housing | casing.   The digital camera which used the noise suppression body of Claims 1-16, or the noise suppression film of Claim 18 inside the housing | casing.   A mobile phone using the noise suppression body according to claim 1 or the noise suppression film according to claim 18 inside a casing.

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