JP2008021990A - Electromagnetic interference suppressor and electromagnetic interference suppression method - Google Patents

Abstract

An object of the present invention is to provide an electromagnetic interference suppressor having an excellent electromagnetic interference suppression effect in a sheet-like electromagnetic interference suppressor obtained by applying and drying a magnetic paint.
A sheet-like electromagnetic interference suppressor obtained by applying and drying a magnetic paint, containing 30 to 80% by volume of soft magnetic powder and 20 to 70% by volume of a binder, and having a temperature of 20 to 60 ° C. The storage elastic modulus (E ′) at 10 is 10 ⁹ Pa or more (JIS K 7244-1). The binder has a number average molecular weight (Mn) of Mn ≧ 1.5 × 10 ⁴ and a storage elastic modulus (E ′) of 10 ⁷ Pa (JIS K) containing no solvent and filler at 20 to 60 ° C. 7244-1) or higher elastomer or resin.
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Description

  The present invention relates to an electromagnetic interference suppressing body used for suppressing electromagnetic interference caused by interference of unnecessary electromagnetic waves in an electronic device, and an electromagnetic interference suppressing method using the same.

  In recent years, various electronic devices such as home electric appliances such as televisions, computers such as personal computers, mobile communication devices such as mobile phones, and medical devices have been widely used. Unwanted electromagnetic waves emitted from these electronic devices It adversely affects electronic devices and causes malfunctions. Therefore, in such an electronic device, an electromagnetic interference suppressor that removes or shields unnecessary electromagnetic waves is used.

  In recent years, the electronic devices have been rapidly increased in speed, weight, thickness and size, and the mounting density of electronic components on a circuit has been dramatically increased. For this reason, along with an increase in electromagnetic noise caused by electromagnetic interference between components and circuit boards, there is a high possibility that electromagnetic interference due to unnecessary electromagnetic waves occurs between components and circuit boards in an electronic device.

As one of the countermeasures for suppressing electromagnetic interference, Patent Document 1 discloses that a sheet-like electromagnetic interference suppressor in which soft magnetic powder is dispersed in a binder is disposed in the vicinity of an electronic component or a circuit. ing.
In using such an electromagnetic interference suppressor, a sheet having high magnetic permeability is required in the region of several tens of MHz to several GHz. It is known that a high magnetic permeability uses a soft magnetic powder having a flat shape rather than a spherical shape, and this flat soft magnetic powder is oriented along the surface of the electromagnetic interference suppression sheet (Patent Literature). 2).

  In order to facilitate orientation, it is preferable to use a material having high fluidity as the matrix material. For example, Patent Document 2 discloses a technique in which a magnetic coating material obtained by dissolving a flat soft magnetic powder and a polymer binder in an organic solvent is coated on a peelable support by a doctor blade method and dried to form a sheet. Are listed. However, when this processing method is used, the solvent in the magnetic paint foams during drying, which causes a problem that a large amount of pores are formed in the sheet. When a large number of holes are generated, the electromagnetic interference suppression effect is greatly reduced. Therefore, it is desirable to fill the soft magnetic powder with high density while minimizing the generation of holes.

  On the other hand, in Patent Document 3, in a method for producing a composite magnetic body in which a mixture obtained by mixing and kneading flat soft magnetic powder and a binder is sheet-formed by a predetermined method, the binder has a glass transition point. A method for producing a composite magnetic body comprising a vinyl chloride resin at 50 ° C. or higher is described. However, in this method, in order to increase the density of the obtained composite magnetic body, a step of pressing the sheet after film formation and solvent removal with a rolling apparatus using a press or a roll is required.

Japanese Patent Laid-Open No. 7-212079 JP 2003-229694 A JP 2001-126910 A

Post-process (pressing process) such as pressing process and calendering process applies shearing force to the sheet by pressing, etc. to discharge the voids in the sheet, and it is also a sufficient binder for narrow gaps between fillers By promoting the flow of the sheet, close packing was realized and the specific gravity of the sheet was greatly improved. This post process is an important process in optimizing the material constants (ε ′, ε ″, μ ′, μ ″) of the sheet. However, when a press process or the like is introduced, there is a drawback that the manufacturing cost increases greatly.
Therefore, conventionally, there has been a demand for obtaining a high-performance sheet-like radio wave interference suppressing body only by a coating process.

The sheet-like radio wave interference suppressor can be manufactured by preparing a solution in which a binder is dissolved in a solvent, mixing and stirring the soft magnetic powder therein, applying it to a support material with a coating apparatus, and drying it. . In order to obtain a state in which no air (solvent trace) remains in the sheet in the above steps, (a) a method of reducing the amount of air entering the coating liquid, and (b) reducing the residual amount of air after coating. It can be divided into methods. For (a), (1) Minimize the amount of solvent when designing the coating solution, (2) No foaming during stirring and coating (minimize initial contamination), (3) Vacuum immediately before coating For (b), the volatilization rate of the solvent is the same as or faster than the sheet drying and solidification rate.
In an actual manufacturing process, in order to increase the manufacturing speed, a method of passing through a heating zone immediately heated to high temperature after coating is air-dried. As a result, the sheet drying rate> solvent volatilization rate, and in particular, since a film is created only on the surface layer where heat is transferred first, the internal air (solvent) is not completely removed, and voids are generated inside the sheet itself. There was a problem that the specific gravity did not increase.

  The subject of this invention is providing the electromagnetic interference suppression body which has the outstanding electromagnetic interference suppression effect in the sheet-like electromagnetic interference suppression body obtained by apply | coating and drying a magnetic coating material. More specifically, the present invention is obtained only by the coating and drying process, does not require a post-process such as a press process or a calendar process, and has the same high performance (high specific gravity and thereby) as when the post-process is performed. It is to provide an electromagnetic interference suppressor having a real part μ ′ and / or an imaginary part μ ″) of the optimum complex relative permeability to be achieved.

  The inventors of the present invention particularly focused on (b) described above and studied how to make air (solvent) escape faster. As a result, the present inventors can suppress the decrease in the electromagnetic interference suppression effect due to the influence of the pores and simply increase the density by simply applying and drying the magnetic paint, and suppress the electromagnetic interference caused by the interference of unnecessary electromagnetic waves. We succeeded in obtaining a useful electromagnetic interference suppressor.

That is, the electromagnetic interference suppressing body of the present invention for solving the problems has the following configurations (1) to (9).
(1) A sheet-like electromagnetic interference suppressor obtained by applying and drying a magnetic paint, containing 30 to 80% by volume of soft magnetic powder and 20 to 70% by volume of a binder at 20 to 60 ° C. An electromagnetic interference suppressor having a storage elastic modulus (E ′) of 10 ⁹ Pa or more (JIS K 7244-1).
(2) A sheet-like electromagnetic interference suppressor obtained by applying and drying a magnetic paint, comprising 30 to 80% by volume of soft magnetic powder and 20 to 70% by volume of a binder, An electromagnetic interference suppressor characterized by being an elastomer or a resin having Mn ≧ 1.5 × 10 ⁴ and a storage elastic modulus (E ′) at 20 to 60 ° C. of 10 ⁷ Pa (JIS K 7244-1) or more. .
(3) The electromagnetic interference suppressor according to (1) or (2), wherein the sheet-like electromagnetic interference suppressor is manufactured without being substantially pressurized.
Here, “without substantially pressurizing” means that it was manufactured without being pressurized under high pressure such as pressing or calendering. For example, at the time of manufacture, storage, storage The unavoidable pressurization that the product or its intermediate body receives by rolling or loading is not included. Similarly, a simple calendar at low pressure is not included.
(4) The electromagnetic interference suppressor according to any one of (1) to (3), wherein the binder is crosslinked.
(5) The real part (μ ′) of the complex relative permeability is 5 or more or the imaginary part (μ ″) is 5 or more at the frequencies of 100 MHz and 1 GHz. The electromagnetic interference suppression body in any one.
(6) The electromagnetic interference suppressor according to any one of (1) to (5), wherein the imaginary part (ε ″) of the complex relative dielectric constant is 500 or less at frequencies of 100 MHz and 1 GHz.
(7) The electromagnetic interference suppressor according to any one of (1) to (6), wherein flame retardancy is imparted.
(8) The electromagnetic interference suppressor according to any one of (1) to (7), which has an adhesive layer or an adhesive layer on at least one surface.
(9) A KEC method at 10 MHz to 1 GHz, comprising a conductive reflective layer and the electromagnetic interference suppressor according to any one of (1) to (8) provided on at least one surface of the conductive reflective layer. Or the magnetic shielding sheet | seat characterized by the magnetic field shielding property obtained by the Advantest method being 10 dB or more.
The electromagnetic interference suppression method of the present invention is characterized in that the electromagnetic interference suppression body is disposed in or around an electronic device.

According to the electromagnetic interference suppressing body of the present invention, according to the above (1) to (4), an elastomer or a resin having a predetermined storage elastic modulus is used as a binder. There is an effect that a decrease in the interference suppression effect is suppressed and the density can be increased, and an excellent electromagnetic interference suppression effect can be obtained.
According to the above (5), since it has a predetermined complex relative permeability at frequencies of 100 MHz and 1 GHz, it can absorb and attenuate electromagnetic waves in the frequency range, and suppress unnecessary radiation noise and the like with respect to the electromagnetic waves. be able to.
According to said (6), since it has the value of the imaginary part of the predetermined complex relative permittivity at the frequencies of 100 MHz and 1 GHz, the electromagnetic interference suppressor itself has low conductivity or high resistivity at that frequency. Has the effect of not reflecting electromagnetic waves.
According to said (7), if the electromagnetic interference suppression body is provided with flame retardance, it can be applied suitably also to the use for which flame retardance is requested | required. For example, electronic information transmission devices including mobile phones, personal computers, and other electronic devices may be required to have flame retardancy.
According to the above (8), when the pressure-sensitive adhesive layer or the adhesive layer is provided on the surface of the electromagnetic interference suppressor, the electromagnetic interference suppressor can be attached to another article, thereby attaching the electromagnetic interference suppressor. Becomes easier.
According to said (9), the sheet | seat obtained by laminating | stacking an electroconductive reflection layer with the electromagnetic interference suppression body of this invention has an effect that an insulation, magnetic shielding property, and a noise suppression effect are acquired.
Therefore, according to the electromagnetic interference suppressing method of the present invention, the electromagnetic interference suppressing body of the present invention is disposed in or around the electronic equipment, so that electromagnetic interference caused by interference of unnecessary electromagnetic waves can be suppressed.

  The electromagnetic interference suppressor of the present invention is mainly used in the form of a (thin magnetic) sheet, with soft magnetic powder and a binder as main constituent materials. The electromagnetic interference suppressor of the present invention is mainly composed of a binder and a filler. A filler here is a general term for all components other than binders, such as a soft magnetic powder, a crosslinking agent, a dispersing agent, a flame retardant, a flame retardant adjuvant, and a plasticizer. In addition, the magnetic paint is obtained by applying a component of the electromagnetic interference suppressor with a solvent, and when the processing step is completed, the solvent is dried and discharged from the sheet.

  Examples of the soft magnetic powder include magnetic stainless steel (Fe-Cr-Al-Si alloy), sendust (Fe-Si-Al alloy), permalloy (Fe-Ni alloy), silicon copper (Fe-Cu-Si alloy), Fe-based alloys such as Fe-Si alloy, Fe-Si-B (-Cu-Nb) alloy, Fe-Ni-Cr-Si alloy, Fe-Si-Cr alloy, Fe-Si-Al-Ni-Cr alloy, etc. All are listed. Further, ferrite or pure iron particles may be used. Amorphous alloys (Co-based, Fe-based, Ni-based, etc.), non-amorphous alloys (Co-based, Fe-based, Ni-based, etc.), electromagnetic soft iron, and Fe-Al based alloys can also be used. They may be oxides or may have an oxide structure in part. Examples of the ferrite include soft ferrite such as Mn—Zn ferrite, Ni—Zn ferrite, Mn—Mg ferrite, Mn ferrite, Cu—Zn ferrite, and Cu—Mg—Zn ferrite, or hard ferrite that is a permanent magnet material. . Examples of iron-based oxides include magnetite. As the Co-based oxide (Co-Zr-O-based, Co-Pb-Al-O-based, or the like), a granular film can be used. Examples of Fe pure iron particles include carbonyl iron powder. The shape of the soft magnetic powder (spherical, flat, fibrous, etc.) is not limited, but it is preferable to use a flat soft magnetic powder with high magnetic permeability. However, in the flat shape, air (solvent) inside the sheet is less likely to escape, and the specific gravity after drying tends not to increase. These magnetic materials may be used alone or in combination. The average particle diameter of the soft magnetic powder or the long diameter of the flat soft magnetic powder is 1 to 300 · m, preferably 20 to 100 · m. The aspect ratio of the flat soft magnetic powder is 2 to 500, preferably 10 to 100. The average particle size is a value obtained by measuring with a particle size distribution measuring device.

  The surface of the soft magnetic powder is preferably surface-treated as necessary. As the surface treatment, in addition to a general treatment such as a coupling agent treatment or a surfactant, resin coating may be performed. Thereby, since affinity with the binder mentioned later improves, soft magnetic powder can be filled with high density. Examples of the coupling agent include a silane coupling agent, a titanium coupling agent, an aluminate coupling agent, an amino coupling agent, a cationic coupling agent, and a nonionic coupling agent. The amount should be about 0.01 to 5% by weight based on the soft magnetic powder. Examples of the resin to be coated with the resin include elastomers and resins (for example, thermoplastic elastomers and various plastics) that are the same as the binder used or have excellent affinity with the binder used. As this elastomer and resin, the same thing as what is illustrated with the binder mentioned later is mentioned. The coating amount of the resin is preferably about 0.01 to 10% by weight with respect to the soft magnetic powder. Further, the surface of the soft magnetic powder may be surface-treated with other additives in addition to the above-described coupling agent treatment and resin coating. The treatment amount in this case is preferably about 0.01 to 10% by weight with respect to the soft magnetic powder. Examples of other surface treatment materials include silica, Si-based compounds, organometallic composites, and metal oxides. By coating the soft magnetic powder with these, it is possible to improve the dispersibility and increase the electric resistance value of the electromagnetic interference suppressor. By adding ZnO, a Zn-based oxide, and an oxide film, an increase in the electrical resistance value and an improvement in corrosion resistance of the electromagnetic interference suppressor can be obtained.

As the binder of the present invention, an elastomer or a resin can be used. Examples of the elastomer include a chlorinated polyethylene, a chlorine type such as vinyl chloride, a polystyrene type such as an SBS type polymer, and a polyolefin type such as EPDM. , Various elastomers (including thermoplastic elastomers) such as polyurethane, polyester, polyamide, fluorine, and silicone. The type of rubber material is not limited, but a material satisfying the numerical range of storage elastic modulus can be used.
Examples of the resin include polyester urethane resin (adipate, carbonate, caprolactam ester, etc.), polyether urethane resin, polyvinyl acetal resin, polyethylene, polypropylene, AS resin, ABS resin, polystyrene, polyvinyl chloride, poly Vinylidene chloride, polyvinyl acetate, ethylene-vinyl acetate copolymer, fluorine resin, acrylic resin, methacrylic ester resin, synthetic resin copolymerized with acrylic acid monomer and other monomers, nylon, polycarbonate, polyethylene terephthalate, polyethylene Phthalate, polybutylene terephthalate, polybutadiene resin, alkyd resin, unsaturated polyester, polysulfone, polyurethane resin (all other than those described above except polyester and polyether) Type), urea resin, imide resin, phenol resin, urea resin, epoxy resin, silicone resin, melamine resin, acrylic resin, acrylic copolymer system, alkyl acrylic resin, ionomer resin, biodegradable resin, recycled resin, etc. These thermoplastic resins or thermosetting resins can be mentioned. These elastomers or resins may be used alone, or may be used after modification (grafting, copolymerization, chemical treatment, etc.), or in a composite system (blend, polymer alloy, composite, etc.) It can also be used. It can also be blended in acrylic silicone, acrylic urethane, acrylic lacquer, various primers, fluorine paint, silicone paint, UV paint, paint. These elastomers and resins have a functional group (such as a polar group such as a glycidyl group, a carboxyl group, a sulfonic acid group, a maleic acid group, an amino group, etc., for example, a metal salt or a quaternary amine to improve cohesion. A polar group capable of forming an ionomer).

The binder in the present invention has a storage elastic modulus (E ′) of 10 ⁷ Pa (JIS K 7244-1) or more in a state not containing a solvent and a filler described later at room temperature (for example, when drying at room temperature at 25 ° C.). It is. When drying at room temperature (for example, 25 ° C.), the storage elastic modulus (E ′) at that temperature is preferably 10 ⁷ Pa or more. Preferably, the storage elastic modulus (E ′) at room temperature is 10 ⁸ Pa or more. In the binder and filler system (electromagnetic interference suppressor product), the storage elastic modulus (E ′) at room temperature is preferably 10 ⁹ Pa or more. In the sheet containing the binder and the filler, it is more preferable that the storage elastic modulus (E ′) at room temperature is 10 ⁹ Pa or more. In order to cope with forced drying (for example, 50 ° C. or more), for example, the storage elastic modulus (E ′) in the state containing no solvent and filler is preferably 10 ⁷ Pa or more even at 55 ° C. Preferably, 10 ⁸ Pa or more is preferable. In other words, the storage elastic modulus (E ′) is preferably 10 ⁷ a or more at 20 to 60 ° C., preferably 25 to 55 ° C., which is a room temperature drying to forced drying temperature range. In the sheet containing the binder and the filler, for example, the storage elastic modulus (E ′) at 55 ° C. which is the drying temperature is preferably 10 ⁹ Pa or more. This is the stage in which the solvent escapes from the magnetic paint (coating liquid) in the solvent volatilization stage, and the binder (polymer) itself exhibits high cohesive force, thereby spontaneously discharging the solvent from the binder. It is for promoting. In general, the storage elastic modulus (E ′) of a sheet tends to decrease with increasing temperature. The sheet containing the binder and filler of the present invention after drying has a storage elastic modulus (E ′) at least at room temperature (25 ° C. is applied) or at room temperature and drying temperature (55 ° C. is applied). It can be said that the value of 10 ⁹ Pa or more is applicable. In forced drying, it is preferable that the storage elastic modulus (E ′) of the binder at the forced drying temperature and the storage elastic modulus (E ′) of the binder at room temperature are not so different. This is to stabilize the cohesive force (solvent discharging ability from the sheet) of the binder accompanying these temperature changes.
The presence of the filler also contributes to the improvement of the storage elastic modulus E ′. Even in room temperature drying or forced drying, air (solvent) is spontaneously and rapidly discharged from the coating liquid (hereinafter referred to as air (solvent) discharge effect), and binders or electromagnetic interference suppressors in those temperature ranges We are also paying attention to the elastic modulus. The dynamic elastic modulus (storage elastic modulus) E ′ of the sheet is a value measured using a tension jig of a dynamic viscoelasticity measuring device. Moreover, the frequency which gives tensile deformation is 1 Hz-100 Hz.

In the drying temperature of the coating liquid, if there is a solvent (i.e. coating liquid) dynamic viscosity of (dynamic viscosity which is obtained by rheometer eta 'is, at a shear rate ^{10 0 ~10 3 sec -1, 10} 0 ~ Compared to 10 ⁵ Pa · s), when the storage elastic modulus (E ′) of the binder in the absence of the solvent (when dried) increases to 10 ⁹ Pa or more, the effect of only solvent drying Even when no temperature difference was given, it was found that the difference between η ′ and E ′ was increased by solvent drying (solvent discharge), so that it had air (solvent) discharge ability.
In other words, the solvent discharge due to drying of the coating liquid is caused by an increase in the elastic modulus of the binder itself that constitutes the coating liquid accompanying the decrease in the solvent, with or without temperature change. In addition, the solvent is uniformly discharged from the inside. Since the elastic modulus of the binder in the absence of a solvent is large, the cohesive force of the binder becomes strong, air (solvent) is discharged, and the actual specific gravity of the sheet increases. Measures by increasing the storage modulus (E ') near the room temperature of the sheet are based on the drying conditions when the coating is naturally dried (dried at room temperature) without forced drying (drying with hot air) after coating. Therefore, increasing the cohesive strength of the binder (increasing the elastic modulus of the binder near room temperature) increases the actual specific gravity of the sheet after natural drying. The room temperature in this case is 2-40 degreeC, for example.

Next, measures to increase the actual specific gravity of the sheet in forced drying will be described. Gelation process (state change process) of coating liquid (with solvent) and solid (dry state) depends on time of dynamic viscoelastic change (using shearing jig) (although some heating temperature is applied, constant temperature) When the change in shear modulus (G ′) and loss modulus (G ″) is followed, the drying speed of the solvent is reflected in the degree of increase in shear modulus (G ′), When the elastic modulus (G ′) increases rapidly and is large, it is fixed while maintaining a high-density dispersion without causing sedimentation of the filler. The elastic modulus (E ′) also increases, however, as described above, this effect does not work sufficiently when only the outer peripheral surface is first heated and cured in heat drying. The storage modulus (E ') of the binder to achieve reliably And limits the boiling point of the solvent.
The restriction on the boiling point of the solvent here means that, in order to stabilize the evaporation rate of the solvent, it is better to volatilize by drying at a temperature below the boiling point not depending on external heating, so the boiling point is forced to dry from room temperature. Do not use a solvent in the temperature range (eg 55 ° C.). Do not fall below the forced drying temperature (eg 55 ° C.). If the drying temperature is higher than the boiling point of the solvent, if excessive solvent remains on the sheet, the solvent will boil, which causes air marks (voids) and lowers the specific gravity of the sheet. I will let you. In addition, drying at a high temperature above the boiling point of the solvent can provide rapid drying. It will be sealed, and residual air (air gap) will be generated by such aggregation. Therefore, it is desirable to perform forced drying at a temperature lower than the boiling point of the solvent in order to promote the spontaneous discharge of the solvent at least in the introduction part (drying initial stage) of the drying furnace. Specifically, the forced drying temperature is about 1 to 100 ° C., preferably about 25 to 75 ° C. lower than the boiling point of the solvent. The drying time is a time sufficient for the solvent to be almost completely discharged, and is usually about 0.5 minutes to 1 hour, preferably about 1 minute to 20 minutes.

The storage elastic modulus (E ′) of the binder is 10 ⁷ Pa or more when dried at room temperature, and it is desirable to maintain this value even at a forced drying temperature (eg, 55 to 60 ° C.). At this time, a glass transition point or a softening point may exist in this temperature range or a lower temperature range, and the storage elastic modulus (E ′) may be 10 ⁷ Pa or more. At this time, in the range from room temperature to forced drying temperature, when the solvent is absent (when dried), the electromagnetic interference suppressor has a low storage elastic modulus (E ′) (for example, E ′ is 10 ⁶ at room temperature). In the case of Pa or less), the air discharge capacity is low and the specific gravity is not sufficiently increased, and a sheet having a high actual specific gravity cannot be obtained only by the coating intended in the present invention. By increasing the molecular weight of the binder, the entanglement of the molecules, the network concentration, etc., to a level that shows insolubility or insolubility in a solvent that cannot be used as a magnetic paint, a larger solvent can be obtained with the same binder amount. The effect of discharging ability can be obtained. In order to increase the storage elastic modulus (E ′) of this binder, it is effective to increase the number average molecular weight (Mn), the weight average molecular weight (Mw), and the molecular weight distribution (Mw / Mn). Also, by increasing the softening point, a high storage elastic modulus (E ′) tends to be obtained even at a high temperature. The high storage modulus (E ′) value of this binder is not only the solvent drying effect, but also the proximity of any other molecule such as the increase in the molecular weight of the binder, the intermolecular force of the molecule, or the chemical reaction such as cross-linking. It can also be obtained by means capable of substantially maintaining the state.

The binder has a number average molecular weight (Mn) of 1.5 × 10 ⁴ or more. Preferably it is 1.8 × 10 ⁴ or more. When the number average molecular weight (Mn) is 1.5 × 10 ⁴ or more, the storage elastic modulus (E ′) of the binder increases, and the actual specific gravity increases. However, when it is less than 1.5 × 10 ⁴ , the storage elastic modulus (E ′) is lowered and the actual specific gravity is lowered, which is not preferable.
The molecular weight distribution {Mw (weight average molecular weight) / Mn (number average molecular weight)} of the binder is preferably 2.4 or more. If the molecular weight distribution is less than 2.4, the actual specific gravity decreases, which is not preferable.
When two or more types of elastomers or resins are mixed and used as a binder, the above number average molecular weight (Mn) and molecular weight distribution (Mw / Mn) are satisfied when each elastomer or resin is mixed. It is preferable.
The Mn and Mw can be measured using a known molecular weight measuring device such as a gel permeation chromatography (GPC) method or a molecular weight measuring device by a light scattering method.
In addition to the molecular weight and molecular weight distribution, the elastomer or resin has a glass transition point and / or a softening point of 50 ° C. or higher, preferably 50 to 280 ° C., more preferably 80 to 220 ° C. When the glass transition point and / or softening point is less than 50 ° C., the actual specific gravity decreases as described later, which is not preferable. The meaning that the softening point is 50 ° C. or higher is that there is no glass transition point and / or softening point in the solvent drying temperature range, and this is particularly effective in the case of room temperature drying without heating or blowing. A higher softening point than the drying temperature for forced drying also contributes to an improvement in actual specific gravity. A more preferable relationship is that drying temperature <solvent boiling point ≦ softening temperature.
The glass transition point and softening point in the present invention are values obtained by measuring the elastomer or resin with DMA (dynamic viscoelasticity measuring device) or a method described later.

The binder is preferably cross-linked. It is also possible to complete the crosslinking reaction by adding a crosslinking agent to the coating liquid and applying it before gelation, and then performing aging by adding heat or the like. For example, aging is performed at 40 to 100 ° C. for about 24 to 96 hours. A known means can be adopted as a means for crosslinking. By crosslinking, the binder can increase the value of the storage elastic modulus (E ′) described above, and can effectively act on the solvent discharge. By crosslinking, the specific gravity is increased, and the durability particularly in a high temperature and high humidity atmosphere is improved.
As a crosslinking agent for crosslinking the binder, for example, a peroxide, sulfur, a phenol resin compound, an isocyanate compound, a metal ion, an amine compound, a quaternary ammonium, or the like, an appropriate kind according to the kind of the binder is used. Can be used. Preferred are peroxides, such as dicumyl peroxide, t-butyl cumyl peroxide, 痾.畚 quote-bis (t-butylperoxy) diisopropylbenzene and the like can be used. The addition amount of the crosslinking agent is 0.1 to 50 parts by weight, preferably 20 to 40 parts by weight with respect to 100 parts by weight of the binder. The crosslinking reaction may be achieved by, for example, light irradiation, UV irradiation, electron beam irradiation, or the like. Moreover, these crosslinking agents can be applied to elastomers or plastics by an appropriate combination. In addition to chemical reactions such as crosslinking, the same effect can be obtained by taking any other means such as physical restraint, which can approach and maintain the state of all other molecules.

The above is a measure to increase the actual specific gravity in the drying stage (room temperature drying and forced drying) after the coating process, but as described above, the higher the viscosity before coating, the higher the magnetic coating material is. The amount of solvent can be reduced, and there is a tendency that solvent marks (air) generated in the drying process are reduced. In order to easily obtain the air (solvent) discharge effect, coating using a high-viscosity magnetic paint is desired. A preferred viscosity range is 10 ³ to 10 ⁶ cps (B-type viscometer), more preferably 10 ⁴ to 10 ⁵ cps (B-type viscometer).

  The concept for increasing the specific gravity after drying of the coated sheet in the present invention is as follows. If the coating liquid is roughly a three-component system of binder / magnetic powder / solvent, it becomes a two-component system of binder / magnetic powder after drying. Among these solvents, the solvent has an affinity for the binder, but does not chemically bond, and will eventually disappear due to the mobility and volatility of the solvent. It is the method of the present invention that this discharge is performed as naturally and rapidly as possible. Specifically, it should be formulated so that the cohesive strength of the binder can be increased so that the solvent can be discharged quickly, and the outer surface and the interior can be dried as uniformly as possible when drying the sheet. In addition, the solvent moving from the inside of the sheet is continuously discharged as long as possible on the outer surface of the sheet, and is lower than the boiling point or azeotropic point of the solvent so as not to leave air marks or voids inside the sheet. State to dry at temperature.

  When these measures are executed, the actual specific gravity of the sheet after coating and drying increases. In particular, even when passing through the drying zone of an actual coating machine at an increased coating speed (corresponding to the forced drying described above), a sheet having a high actual specific gravity can be obtained. Therefore, the pressurization process performed conventionally is unnecessary. However, for the purpose of complementing the insufficient orientation of the soft magnetic powder, a pressurizing process that adds a simple calendar process may be combined as necessary.

  The blending ratio of the soft magnetic powder and the binder is preferably 30 to 80% by volume of the soft magnetic powder and 20 to 70% by volume of the binder, 40 to 70% by volume of the soft magnetic powder and 30 to 60% by volume of the binder. It is more preferable that When the content of the soft magnetic powder is less than 30% by volume and the content of the binder exceeds 70% by volume, a desired electromagnetic interference suppressing effect cannot be obtained. On the other hand, when the content of the soft magnetic powder exceeds 80% by volume and the content of the binder is less than 20% by volume, the obtained electromagnetic interference suppressor becomes brittle, so that processing becomes difficult.

The electromagnetic interference suppressor of the present invention preferably has an actual specific gravity / theoretical specific gravity of 0.5 or more. Solvents are not included in this theoretical specific gravity calculation. In the calculation, it is assumed that the solvent is completely dried out. If the actual specific gravity / theoretical specific gravity is less than 0.5, a large amount of holes are present inside the electromagnetic interference suppressor, so that the effect of the electromagnetic interference suppressor decreases. Here, the actual specific gravity is a value obtained from the weight / volume of the produced electromagnetic interference suppressor, and the theoretical specific gravity is obtained by dividing the sum of specific gravity × content of each component by volume. When the electromagnetic interference suppressor is configured to be thin or the like, the theoretical specific gravity value is in the range of 2.5 to 7.
If air remains in the interior and voids are generated, the effect of the electromagnetic interference suppressor is greatly reduced. Therefore, it is desired to fill the soft magnetic powder with high density while suppressing the generation of voids as much as possible. However, it is difficult to completely discharge the air remaining in the interior, and in reality, residual air (air gap) inevitably remains in the product due to the processing step and the shape and amount of the soft magnetic powder. That is, this state generally means that the specific gravity is lower than the specific gravity (theoretical specific gravity) when there is essentially no air (void).

  Moreover, in order to improve the dispersibility and rust prevention effect of soft magnetic powder, it is preferable to add 0.1 to 10 weight% of dispersing agent with respect to content of soft magnetic powder. As the dispersant, one type or several types of various types can be used. For example, higher fatty acids or higher fatty acid salts can be used alone or in combination. Examples of the higher fatty acid herein include palmitic acid, stearic acid, oleic acid, linoleic acid, and linolenic acid. The higher fatty acid or higher fatty acid salt preferably has 10 or more carbon atoms, more preferably 14 to 20 carbon atoms. Both saturated higher fatty acids and unsaturated higher fatty acids can be used, but saturated higher fatty acids are preferred for stability. Examples of higher fatty acid salts include aluminum salts, sodium salts, potassium salts, lithium salts, barium salts, calcium salts, and magnesium salts of these higher fatty acids. When used in combination, the ratio of higher fatty acid / higher fatty acid salt is preferably 10/90 to 90/10 in weight ratio.

In the present invention, among the higher fatty acid metal salts exemplified above, a stearic acid metal salt is preferably used. Specific examples of the metal stearate include cadmium stearate, barium stearate, calcium stearate, zinc stearate, lead stearate, lead stearate, tin stearate, aluminum stearate, magnesium stearate and the like.
When the higher fatty acid metal salt as described above is contained, the surface resistivity and flame retardancy of the electromagnetic interference suppressor are improved, and the dispersibility and rust prevention properties of the soft magnetic metal are improved. The reason why these effects can be obtained is that the higher fatty acid metal salt is dispersed in the electromagnetic interference suppressor so as to cover the surface of the soft magnetic metal in the molding process, and the surface of the soft magnetic metal is densely coated, This is presumably due to the formation of a complex network with other soft magnetic metals.

  The higher fatty acid metal salt may be contained in an amount of 0.01 to 5% by volume, preferably 0.5 to 4% by volume, based on the total volume of the soft magnetic metal. By containing the higher fatty acid metal salt within this range, the above-described effects can be obtained. That is, the surface resistivity of the electromagnetic interference suppressor is improved, and the dispersibility and rust prevention of the soft magnetic metal are improved. On the other hand, if the content is less than 0.01% by volume, the above effect may not be obtained. If the content exceeds 5% by volume, the properties of the binder are diluted. Since the suppression effect may be reduced, it is not preferable.

  The electromagnetic interference suppressor of the present invention has a real part (ε ′), an imaginary part (ε ″) of a complex relative permittivity, and a real part (μ ′) and an imaginary part (μ ″) of a complex relative permeability. ing. The addition of the soft magnetic powder increases the real part μ ′ of the complex relative permeability of the electromagnetic interference suppressor. Further, when the soft magnetic powder is densely oriented, the imaginary part μ ″ of the complex relative permeability increases at a frequency of 50 MHz to 1 GHz. The larger the real part μ ′ of the complex relative permeability, the more the lines of magnetic force (magnetic flux). The smaller the real part μ ′ of the complex relative permeability is, the more the lines of magnetic force (magnetic flux) are less likely to pass through the sheet, and the electromagnetic interference suppressor is an imaginary part of the complex relative permeability. The larger μ ”is, the more magnetic field energy is lost, and the smaller the imaginary part μ” of the complex relative permeability is, the less magnetic field energy is lost. In addition, flat soft magnetic metals are densely oriented and dispersed. Therefore, the capacitor electrode plate becomes closer, the capacity of the capacitor increases, the real part ε 'of the apparent complex relative permittivity increases, and the entire sheet is blended with a large amount of conductive metal. Guidance Sex uplink, the imaginary part of the complex relative permittivity epsilon "is also increased. Here, as shown in FIG. 6, the real part ε ′ of the complex relative permittivity and the imaginary part ε ″ of the complex relative permittivity have a relatively small frequency dependency and are stable. The values of the real part ε ′ of the complex relative permittivity and the imaginary part ε ″ of the complex relative permittivity shown at a certain frequency can be said to be almost representative of the properties of the electromagnetic interference suppressor for all frequencies.

  Furthermore, in the electromagnetic interference suppressor of the present invention, the imaginary part ε ″ of the complex relative permeability dielectric constant ε is as small as 500 or less for electromagnetic waves of 100 MHz and 1 GHz. Specifically, in the case of 100 MHz, the complex ratio The conductivity σ ′ = 2.8 S / m and the resistivity ρ = 0.36 Ω · m are derived from the number of imaginary part ε ″ of the permeability permittivity ε of 500, and the sheet has a lower conductivity than these values. Or since it becomes a high resistivity, it means that there is little electromagnetic wave reflection of the sheet itself. Similarly, in the case of 1 GHz, the conductivity σ ′ = 27.8 S / m and the resistivity ρ = 0.04 Ω · m are derived from the number imaginary part ε ″ of the complex relative permeability dielectric constant ε of 500. Since the sheet has a low conductivity or a high resistivity than the above numerical value, this means that the electromagnetic wave reflection of the sheet itself is small.

  According to the present invention, the electromagnetic interference suppressor has a real part μ ′ of the complex relative permeability μ as small as 5 or more, or an imaginary part μ of the complex relative permeability μ for 100 MHz and 1 GHz electromagnetic waves. 6 is greater than 5. Specifically, for example, tan δ (= μ ″ / μ ′) representing a loss of permeability to an electromagnetic wave of 50 MHz to 1 GHz shown in FIG. It can be seen that the magnetic loss performance is excellent. As a result, a magnetic field line (magnetic flux) passes through the sheet with respect to a magnetic field formed by an electromagnetic wave of 50 MHz to 1 GHz, and energy of the magnetic field can be lost. Therefore, electromagnetic waves of 50 MHz to 1 GHz can be absorbed and attenuated by using the electromagnetic interference suppressor. Therefore, unnecessary radiation noise and the like can be suppressed for electromagnetic waves of 50 MHz to 1 GHz.

  The magnetic shield sheet of the present invention comprises a conductive reflection layer and the electromagnetic interference suppressor provided on at least one surface of the conductive reflection layer, and has a magnetic field shielding property obtained by the KEC method at 10 MHz to 1 GHz. 10 dB or more. Preferably, the magnetic field shielding property obtained by the KEC method at 0.1 MHz to 1 GHz is 10 dB or more. Here, the magnetic shield is a sheet having a property of shielding magnetism. The magnetic field shielding property is superior to the KEC method in which the magnetic leakage to the periphery of the sample is suitably suppressed by devising the sample holder in terms of the configuration of the measuring machine, but the same result can be obtained by the advanced method.

  The magnetic shield sheet of this invention is demonstrated based on drawing. 1A and 1B are cross-sectional views showing an embodiment of the present invention. As shown in FIGS. 1A and 1B, the magnetic shield sheet of the present invention has a magnetic layer 2 provided only on one side of the conductive reflective layer 1 or a magnetic layer 2 provided on both sides. It is. The magnetic layer 2 here is the same as the electromagnetic interference suppressor described above. The conductive reflective layer 1 is composed of a magnetic metal layer, a magnetic ceramic layer, an Fe (iron) -based metal sheet, a Co-based sheet, stainless steel, or Fe-based metal powder and a binder. The conductive reflective layer 1 is a layer having at least conductivity and reflecting electromagnetic waves. The conductive reflective layer 1 may be a plate, sheet, film, foil, woven fabric or non-woven fabric made of a conductive material, or a plate, sheet, film, made of a mixed material obtained by mixing a conductive material with a synthetic resin. It may be a foil, a woven fabric or a non-woven fabric, or may be a plate, sheet, foil, woven fabric or film in which a conductive film made of a conductive material is formed on a base material made of a synthetic resin or the like. General-purpose conductive metals and magnetic metals such as aluminum, copper, silver, gold, iron, and stainless steel may be used as they are, or they may be used as inks, pastes, and adhesives that contain them to develop conductivity. good. The conductive material forming the conductive reflective layer 1 may be a metal or a material other than a metal such as carbon or graphite. As the material of the conductive reflective layer 1, the material exemplified for the soft magnetic powder can be used. The Fe metal sheet is exemplified by a metal foil of Fe or an Fe alloy. Examples of the Fe-based alloy include an Fe-based alloy having at least one element selected from Al, Mg, Co, Ni, Mo, B, Si, Sr, Nb, Cr, and the like. These may be in the form of a sheet or deposited. 1 (c) and 1 (d) are obtained by providing an adhesive layer 3 (adhesive layer or adhesive layer) on one or both sides of the magnetic shield sheet shown in FIGS. 1 (a) and 1 (b), respectively. In FIG. 1B and FIG. 1D, a configuration in which the magnetic layer 2 is used only on one surface and an insulating layer having no magnetism is used on the other surface can be used.

Specific examples of the Fe-based metal sheet and the Fe-based metal powder include SPCC (cold rolled plate and steel strip (JIS G 3141 and JIS G 3313)), SPCD (cold rolled steel plate and strip steel (JIS G 3141)). , SUY (electromagnetic soft iron), amorphous metal foil, hot-dip galvanized steel sheet and the like. Regardless of whether or not heat treatment is applied, the initial permeability measured at the time of use is 10 or more and less than 5,000. In a commercial item, a silver top (SF), Foil Top (made by Toyo Kohan Co., Ltd.) etc. can be used, for example.
These Fe-based metal sheet and Fe-based metal powder preferably have an initial permeability of less than 5,000. In general, a material having an initial permeability of 5,000 or more is limited to permalloy, supermalloy, and the like, and has an initial permeability value that is reached when an appropriate heat treatment is performed. Although their magnetic permeability is high, they are unstable and their magnetic properties are greatly deteriorated in accordance with bending and stress application. That is, high magnetic permeability is achieved at the expense of workability.

  On the other hand, the magnetic shield sheet of the present invention is intended to emphasize workability as long as desired magnetic shield properties can be secured. In other words, the performance is stable even when a secondary process such as punching and bending the magnetic shield sheet is performed. Furthermore, even if an after-curing step for increasing the magnetic permeability is omitted, desired magnetic shielding properties can be exhibited.

When the conductive reflective layer 1 is composed of Fe or Fe-based alloy powder, the Fe or Fe-based alloy powder may be mixed with a binder and formed into a sheet shape. At this time, the Fe or Fe-based alloy powder is about 20 to 90% by volume, preferably 40 to 80% by volume, based on the total amount. For example, it is used in the properties of magnetic paint.
The thickness of the conductive reflective layer 1 is preferably 500 μm or less, and particularly preferably 1 μm to 100 μm. The conductive reflective layer 1 is not limited to a plate, foil, paint, or the like, and may be one that is plated on a mesh, nonwoven fabric, or the like, or may be fixed by vapor deposition, plating, adsorption, or the like.
The magnetic shield effect is required to be 10 dB in the frequency range of 500 KHz to 1 GHz by a known method called the KEC method or the Advantest method. Preferably it is 20 dB or more. In this frequency range, the desired magnetic shield effect (10 dB) cannot be obtained with the single layer configuration of the magnetic layer 2, and the conductive reflective layer 1 is laminated.

  According to the present invention, a sheet having insulating properties, magnetic shielding properties, and noise suppressing effects can be obtained by laminating the conductive reflective layer 1 and the electromagnetic interference suppressing body 2. The magnetic layer 2 also has an effect as a rust preventive agent for the conductive reflective layer 1. Further, the conductive reflective layer 1 can be subjected to an adhesive treatment or an adhesion treatment as necessary.

Moreover, it is preferable that the electromagnetic interference suppression body of this invention has added the flame retardant or the flame retardant adjuvant. This imparts flame retardancy to the electromagnetic interference suppressor. For example, an electronic device such as a mobile phone may be required to have flame retardancy for an interior polymer material.
The flame retardant for obtaining such flame retardancy is not particularly limited. For example, phosphorus compounds, boron compounds, bromine flame retardants, zinc flame retardants, nitrogen flame retardants, hydroxide series Flame retardants, metal compound flame retardants, and the like can be used as appropriate. Examples of phosphorus compounds include phosphate esters and titanium phosphate. Examples of the boron compound include zinc borate. Examples of brominated flame retardants include hexabromobenzene, hexabromocyclododecane, decabromobenzyl phenyl ether, decabromobenzyl phenyl oxide, tetrabromobisphenol, ammonium bromide and the like. Examples of the zinc-based flame retardant include zinc carbonate, zinc oxide, and zinc borate. Examples of nitrogen-based flame retardants include triazine compounds, hindered amine compounds, or melamine compounds such as melamine cyanurate and melamine anidine compounds. Examples of the hydroxide flame retardant include magnesium hydroxide and aluminum hydroxide. Examples of the metal compound flame retardant include antimony trioxide, molybdenum oxide, manganese oxide, chromium oxide, and iron oxide. As for the combination and amount of the flame retardant and the flame retardant auxiliary, an appropriate combination and amount are selected in order to obtain the desired flame retardancy, but even when excluding the substances subject to the RoHS directive, the flame retardant equivalent to UL94V0 is sufficiently obtained. It is possible to get sex.

  In this embodiment, in the UL94 flame retardant test, the binder is 100, the bromine-based flame retardant is 20, the antimony trioxide is 10 and the phosphate ester is 14 in a weight ratio. Flame retardance equivalent to V0 can be obtained. The electromagnetic interference suppressor can be suitably used as a material constituting such an article or by being attached to the article. For example, it can be suitably used by being mounted on an article used in a space or the like where it is desired to prevent and suppress combustion and the generation of gas accompanying it, such as an aircraft, a ship, an automobile, and a device in a vehicle.

The electromagnetic interference suppressor of the present invention is not limited to the above-mentioned additives other than the binder and soft magnetic powder, and any additives such as inorganic fillers, fine powders, and gel substances are added as necessary. be able to. The added additive is a filler referred to in the present invention.

  As for the electromagnetic interference suppression body of this invention, at least one surface part has adhesiveness or adhesiveness. In this embodiment, it has a sticking layer (adhesive layer or adhesive layer), and as a result, as shown in FIGS. 1 (c) and 1 (d), FIG. The adhesive layer 3 is provided on one side. The electromagnetic interference suppressor 2 can be attached to the article by the bonding force due to the adhesiveness or adhesiveness of the adhesive layer 3. Therefore, the electromagnetic interference suppressing body 2 can be easily provided between the antenna element and the metal member, for example, by sticking to the metal member. The electromagnetic interference suppressing body 2 is provided with one side in the thickness direction arranged on the antenna element side and the other side in the thickness direction arranged on the metal member side. As the adhesive material, for example, No. manufactured by Nitto Denko Corporation. 5000 NS is used.

  The electromagnetic interference suppressor of the present invention is preferably used in the form of a (thin magnetic) sheet having a thickness of 1 μm to 2 mm. More preferably, it is a sheet having a thickness of 10 μm to 1 mm. In general, in the case of a sheet, the (flat) soft magnetic powder aggregates in the inside, and there is no degree of freedom in the passage of air and solvent volatile gases, and voids tend to remain in the sheet. Then, the remaining air in the seat is almost eliminated.

  The electromagnetic interference suppressor of the present invention is a magnetic paint containing the above (flat) soft magnetic powder and a binder, for example, applied to a support with a blade or the like, dried, and then separated (peeled) from the support. Can be obtained.

  For the preparation of the magnetic paint, a (flat) soft magnetic powder and a solvent for dissolving or dispersing the binder are used. Examples of such solvents include, but are not limited to, ketones such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone, and cyclohexanone, alcohols such as methanol, ethanol, propanol, butanol, and isopropyl alcohol, and acetic acid. Esters such as methyl, ethyl acetate, propyl acetate, butyl acetate, ethyl lactate and ethyl glycol acetate, ethers such as diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran and dioxane, and aromatic hydrocarbon compounds such as benzene, toluene and xylene , Halogenated hydrocarbon compounds such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, chlorobenzene, and the like can be used. These solvents can be used alone or in combination of two or more.

The magnetic paint contains the solvent in an amount of 1000 parts by weight or less, preferably 100 to 800 parts by weight, based on 100 parts by weight of the binder. On the other hand, if the solvent content exceeds 1000 parts by weight, residual air remains in the sheet, which is not preferable.
As the dispersion and kneading apparatus for preparing the coating material, for example, a kneader, an agitator, a ball mill, a sound mill, a roll mill, an extruder, a homogenizer, an ultrasonic disperser, a two-axis planetary kneader, or the like can be used. Among these dispersing and mixing apparatuses, an agitator, a ball mill, a roll mill, a homogenizer, an ultrasonic disperser, a twin-shaft planetary kneader, etc. that do not break or give distortion to (flat) soft magnetic powder are particularly preferable.

  The support is not particularly limited. For example, paper, paper laminated with a polymer resin such as polyolefin, paper, polymer, resin, cloth, non-woven fabric, metal, metal-treated (vapor deposition, plating) Etc. Among these, a thin and strong polymer resin is preferable, and examples of the polymer resin include polyesters such as polyethylene terephthalate, polyethylene-2 and 6-naphthalate, polyolefins such as polyethylene and polypropylene, and polyolefins such as these. Fluorine resin in which part or all of hydrogen is replaced with fluorine resin, cellulose derivatives such as cellulose triacetate and cellulose diacetate, vinyl resins such as polyvinyl chloride, vinylidene resins such as polyvinylidene chloride, polycarbonate, polyphenylene sulfide, and polyamideimide And polyimide. The surface of these polymer resins is preferably peeled with a release agent such as a silicone resin because the electromagnetic interference suppressor can be easily peeled off. These polymer resins are preferably in the form of a film having a thickness of about 1 μm to 100 mm. The support may be peeled off and removed from the product, or the support may be provided integrally with the electromagnetic interference suppressor as a final product. If it peels, it can contribute to thickness reduction, and if it integrates, it will contribute to the improvement of the rigidity of an electromagnetic interference suppression body, and workability improvement, such as a slit.

  The method for applying the magnetic paint on the support is not particularly limited, and for example, air doctor coat, blade coat, wire bar coat, air knife coat, squeeze coat, impregnation coat, reverse roll coat, transfer roll coat, Any of conventional methods such as gravure coating, kiss coating, cast coating, extrusion coating, die coating, and spin coating can be employed.

  Further, a magnetic field may be applied during or after coating the magnetic coating material on the support material. Since the electromagnetic interference suppressing body obtained in this way has the flat soft magnetic powder oriented in the in-plane direction, the soft magnetic powder can be filled at a higher density. In order to orient the flat soft magnetic powder in the in-plane direction, for example, a permanent magnet is installed above or below the coated surface, and a magnetic field is added in the vertical direction (the thickness direction of the sheet). The strength of the magnetic field (magnetic flux density) varies depending on the type of the binder and flat soft magnetic powder dissolved or dispersed in the solvent, but is generally in the range of 0.01 to 1 Tesla.

  The end material that has been applied to the support material, dried, and then cut off to form a predetermined shape is collected, peeled off the support, and added to the magnetic paint, for example. Since it is dissolved or dispersed, it can be reused.

  The electromagnetic interference suppressor of the present invention is used in various electronic devices such as home electric products such as televisions, computers such as personal computers, mobile communication devices such as mobile phones, and medical devices, and unnecessary electromagnetic waves emitted from these electronic devices. Can suppress other electronic devices, electronic components, and circuit boards from causing malfunctions. Specifically, electromagnetic interference caused by interference of unnecessary electromagnetic waves is effectively suppressed by being disposed inside or around the electronic devices. It can also be used as a SAR countermeasure component. It can also be conveniently used as a magnetic shield material in the form of a sheet. For this reason, as a usage form of the electromagnetic interference suppressor of the present invention, for example, a sheet-like electromagnetic interference suppressor is appropriately cut out and pasted near the noise source of the device, or as described above near the noise source of the device. It is used, for example, by forming an electromagnetic interference suppressor by coating. Specifically, it may be affixed as a countermeasure against electromagnetic shielding of FPC circuits in electronic equipment.

  Hereinafter, although an electromagnetic interference suppression object of the present invention is explained in detail using an example and a comparative example, the present invention is not limited to the following examples.

The materials used in the following examples and comparative examples are as follows.
-Urethane resin: NIPPOLAN manufactured by Nippon Polyurethane Industry Co., Ltd.-Flat Fe-Ni-Cr-Si: JEM powder manufactured by Mitsubishi Materials Co., Ltd. The solvent used for preparing the coating liquid is a mixed solvent mainly composed of toluene.
The storage elastic modulus (E ′) was measured by DMA (dynamic viscoelasticity measuring device) manufactured by Seiko Instruments Inc. The results of measuring the storage elastic modulus (E ′) of the resin and electromagnetic interference suppressor used in the examples are shown in FIGS. In FIG. 3, since Comparative Example 1 is 1.0 × 10 ⁶ or less, it does not appear in the graph. The softening temperature is a temperature at which the DMA and the sheet-like sample (JIS No. 2 dumbbell shape) are given a constant load weight, heated at 5 ° C./min in a thermostatic bath, and the elongation of the sheet-like sample is maximized. It is decided by.

[Examples 1 to 4 and Comparative Examples 1 and 2]
<Production of electromagnetic interference suppression sheet>
A magnetic paint was prepared by adding a binder and other fillers and a solvent so that the content of the soft magnetic metal powder in the sheet was 40% by volume at the time of drying shown in Table 1, and PET (polyethylene terephthalate, It was coated and dried on a release support), and sheet forming was performed without pressure treatment. Next, the release support was peeled off to obtain an electromagnetic interference suppression sheet having a thickness of 100 μm. In Table 1, the same amount of soft magnetic metal powder is used. What is different is the properties of the polymer used as the binder. In Table 1, Example 3 is obtained by adding a curing agent (TDI isocyanate composition) to the resin of Example 1 and performing aging at 80 ° C. for 72 hours to perform crosslinking. The obtained electromagnetic interference suppression sheet was measured for material constants (μ ′, μ ″, ε ′, ε ″), specific gravity, 1 GHz transmission loss, and 100 MHz transmission loss. The results are also shown in Table 1. The said measurement was performed at room temperature 25 degreeC. The binder used in the examples has the same basic structure of urethane resin, but the number average molecular weight (Mn), weight average molecular weight (Mw), molecular weight distribution (Mw / Mn), ratio of hard segment to soft segment (Table (Not shown). As a result, among the properties of the binder, the storage elastic modulus (E ′) and the softening point are changed, and the influence on the sheet performance is observed.

<Measurement method of molecular weight>
The molecular weight and molecular weight distribution were measured by gel permeation chromatography (GPC) manufactured by Shimadzu Corporation, using polystyrene as a standard substance, and weight average molecular weight (Mw) and number average molecular weight (Mn). The molecular weight distribution was calculated from the obtained Mw / Mn. The measurement conditions for GPC are as follows. Solvent: tetrahydrofuran, solvent flow rate: 1 mL / min, temperature: 40 ° C., sample concentration: 3 mg / mL, sample injection amount: 50 μL, detector: RI. For high molecular weight urethane resins, DMF may be used as a developing solvent.

マイクロストリップラインの伝送損失は電磁干渉抑制体５４の厚みが厚くなるほど高くなる。一般的には、厚みが薄く且つ高伝送損失の電磁干渉抑制体５４が望まれている。 <Measurement method of transmission loss>
A microstrip line with impedance Z = 50Ω was used for measurement of transmission loss. The microstrip line is a method for measuring transmission loss of nearby noise that is widely used due to its structure suitable for mounting surface-mounted components and ease of production. FIG. 5 shows the shape of the microstrip line used. In this device, a linear conductor path 52 is provided on the surface of the insulator substrate 51, and an electromagnetic interference suppression sheet 54 is placed on the conductor path 52. Both ends of the conductor path 52 are connected to a network analyzer (not shown). Then, with respect to the incident wave indicated by the arrow A, the reflection amount (dB) (indicated by the arrow S11) and the transmission amount (dB) (indicated by the arrow S21) from the mounting portion of the electromagnetic wave absorbing material 54 are measured, and these The transmission loss (absorption amount) was calculated from the following equation.

The transmission loss of the microstrip line increases as the thickness of the electromagnetic interference suppressor 54 increases. In general, an electromagnetic interference suppressor 54 having a small thickness and high transmission loss is desired.

<Measurement method of transmission loss>
The degree to which the electromagnetic waves radiated from the oscillation antenna reached the reception antenna in the oscillation and reception loop antennas arranged at intervals of 1 mm through the electromagnetic interference suppression sheet was measured by a network analyzer. This measurement makes it possible to evaluate the attenuation effect of the electromagnetic interference suppression sheet against radiation noise.

表１から、Ｍｎが１．５×１０⁴以上のポリマーを用いた系、また結合剤の貯蔵弾性率Ｅ’が室温乾燥時または強制乾燥時に１０⁷Ｐａ以上である系が、高い比重その他高性能を示している。さらに結合剤及び充填剤からなる電磁干渉抑制体において、乾燥温度（室温乾燥または強制乾燥）にて貯蔵弾性率Ｅ’が１０⁹Ｐａ以上であることにより、良好な溶剤排出効果を発現して、高い比重その他高性能を得ることができる。また表１から、結合剤の分子量分布（Ｍｗ／Ｍｎ）が２．４以下のポリマーを用いた系で、結合剤の貯蔵弾性率Ｅ’が乾燥温度で１０⁷Ｐａ以下である比較例１は、実比重が低く、透磁率が低く、伝送損失、透過損失が低い。また、比較例２では、室温（２５℃）での結合剤の貯蔵弾性率Ｅ’は１０⁷Ｐａ以上であるが、乾燥温度（５５℃）での貯蔵弾性率Ｅ’が１０⁷Ｐａ以下であるため、実比重が低く、透磁率が低く、伝送損失、透過損失が低い。
これに対して、本発明の範囲内である実施例１〜４は、実比重が高く、透磁率が高く、伝送損失、透過損失が高い結果を示した。なお、実施例４では、温度５５℃での結合剤の貯蔵弾性率Ｅ’は１０⁷Ｐａ以下であるが、乾燥時の乾燥温度（２５℃）での貯蔵弾性率Ｅ’が１０⁷Ｐａ以上であるため、結合剤の凝集力は強く、溶剤排出がなされ実比重が高くなった。
貯蔵弾性率に関しては、表１に示すように、２５℃と５５℃の２点を評価していた。これは塗工シートを室温乾燥する場合が、ポリマーの２５℃の貯蔵弾性率が当てはまり、塗工シートを強制乾燥する場合が、ポリマーの５５℃の貯蔵弾性率が当てはまる関係となる。それぞれの乾燥温度において、ポリマーの溶剤排出能力を評価しており、それぞれの温度で高い数値を取るほど、ボイドを発生することが少なく乾燥シートを得ることができる。この溶剤排出能力を高めるためには、溶剤乾燥条件に於けるポリマーの凝集力を高めることが必要であり、本発明では分子量および分子量分布と貯蔵弾性率Ｅ’に注目して適正な範囲を求めた。
実施例３は実施例１の樹脂を用い、架橋剤を添加して磁性塗料としたものである。磁性塗料の段階では架橋反応は起きず、実施例１とほぼ同じ性状の塗液として取り扱うことができる。乾燥時あるいは乾燥後に三次元架橋を施すことにより分子量及び分子量分布は実施例１よりも向上しており、ポリマーの凝集力も貯蔵弾性率も向上できている。 <Evaluation method of material constant>
The material constants of the electromagnetic interference suppressor include a real part μ ′ and an imaginary part μ ″ of complex relative permeability, and a real part ε ′ and an imaginary part ε ″ of complex relative permittivity. The measurement was carried out by ring processing (φ7 × φ3) of the material and the coaxial tube method. The equipment used is a material analyzer (E4991A manufactured by Agilent) for frequencies of 1 MHz to 1.8 GHz.
In Table 1, for example, “2.32E + 07” means 2.32 × 10 ⁷ .

From Table 1, a system using a polymer having Mn of 1.5 × 10 ⁴ or more, and a system in which the storage elastic modulus E ′ of the binder is 10 ⁷ Pa or more at the time of drying at room temperature or forced drying, high specific gravity and other high Shows performance. Furthermore, in the electromagnetic interference suppressor composed of a binder and a filler, when the storage elastic modulus E ′ is 10 ⁹ Pa or more at the drying temperature (room temperature drying or forced drying), a good solvent discharge effect is expressed, High specific gravity and other high performance can be obtained. Further, from Table 1, Comparative Example 1 is a system using a polymer having a binder molecular weight distribution (Mw / Mn) of 2.4 or less, and the storage elastic modulus E ′ of the binder is 10 ⁷ Pa or less at the drying temperature. The actual specific gravity is low, the magnetic permeability is low, the transmission loss and the transmission loss are low. In Comparative Example 2, the storage elastic modulus E ′ of the binder at room temperature (25 ° C.) is 10 ⁷ Pa or more, but the storage elastic modulus E ′ at the drying temperature (55 ° C.) is 10 ⁷ Pa or less. Therefore, the actual specific gravity is low, the magnetic permeability is low, and the transmission loss and transmission loss are low.
On the other hand, Examples 1-4 which are within the scope of the present invention showed high actual specific gravity, high magnetic permeability, and high transmission loss and transmission loss. In Example 4, the storage elastic modulus E ′ of the binder at a temperature of 55 ° C. is 10 ⁷ Pa or less, but the storage elastic modulus E ′ at the drying temperature (25 ° C.) during drying is 10 ⁷ Pa or more. Therefore, the cohesive strength of the binder was strong, the solvent was discharged, and the actual specific gravity increased.
Regarding storage elastic modulus, as shown in Table 1, two points of 25 ° C. and 55 ° C. were evaluated. When the coated sheet is dried at room temperature, the storage elastic modulus of 25 ° C. of the polymer is applied, and when the coated sheet is forcedly dried, the storage elastic modulus of 55 ° C. of the polymer is applied. The solvent discharging ability of the polymer is evaluated at each drying temperature, and the higher the value at each temperature, the less the voids are generated, and the dried sheet can be obtained. In order to increase the solvent discharging capacity, it is necessary to increase the cohesive strength of the polymer under the solvent drying conditions. In the present invention, an appropriate range is obtained by paying attention to the molecular weight, molecular weight distribution and storage elastic modulus E ′. It was.
Example 3 uses the resin of Example 1 and adds a cross-linking agent to make a magnetic paint. The crosslinking reaction does not occur at the magnetic coating stage, and it can be handled as a coating liquid having substantially the same properties as in Example 1. By performing three-dimensional crosslinking during or after drying, the molecular weight and molecular weight distribution are improved as compared with Example 1, and the cohesive strength and storage elastic modulus of the polymer can be improved.

  The electromagnetic interference suppressor of the present invention has a relationship in which the real part μ ′ of the complex relative permeability is high and the imaginary part μ ″ of the complex relative permeability is high at frequencies of 100 MHz and 1 GHz or between them. As shown in Table 1, the electromagnetic interference suppressor (Examples 1 to 4) of the present invention has a property that it is easy to collect a magnetic field because μ ′ is high, and it is easy to lose magnetic flux collected due to high μ ″. It can be said that it has. And since the imaginary part 蜚 of the complex relative permittivity is low (500 or less), it has been found that the electromagnetic interference suppression body itself has low conductivity and high resistivity. That means that the electromagnetic wave interference suppressor itself does not reflect (shield) the electromagnetic wave.

表２、表３から、高温高湿環境下では、電磁干渉抑制シートは適度に架橋されているのがよいことがわかる。 [Examples 5 and 6]
<Production of crosslinked electromagnetic interference suppression sheet>
Except for the blending ratio shown in Table 2, the same material as in Example 3 was used, and the electromagnetic interference suppression of 100 μm in thickness was performed by crosslinking the binder with a curing agent without applying pressure as in Example 3. A sheet was obtained. The obtained electromagnetic interference suppression sheet was measured for material constants (μ ′, μ ″, ε ′, ε ″), specific gravity, 1 GHz transmission loss, and 100 MHz transmission loss. Further, the presence or absence of cracks when the sheet of each example was bent at 90 ° at room temperature was visually observed. The results are also shown in Table 2. Table 2 also shows the test results of Example 3.
Further, the material constants (μ ′, μ ″, ε ′, ε ″), specific gravity when the electromagnetic interference suppression sheets of Examples 3, 5, and 6 were left in an atmosphere of 50 ° C. and 85% humidity for 500 hours. The transmission loss of 1 GHz, the transmission loss of 100 MHz, and the presence or absence of cracks when bent at 90 ° were measured. The results are also shown in Table 3.

From Table 2 and Table 3, it can be seen that the electromagnetic interference suppression sheet should be appropriately crosslinked in a high temperature and high humidity environment.

(A)-(d) is sectional drawing which shows an example of the magnetic shielding sheet using the magnetic interference suppression body of this invention, respectively. It is sectional drawing which shows an example of the electromagnetic interference suppression body of this invention. It is a graph which shows the measurement result of the storage elastic modulus (E ') of resin of this invention. It is a graph which shows the measurement result of the storage elastic modulus (E ') of the electromagnetic interference suppression body of this invention. It is the schematic which shows the shape of the microstrip line used for the measurement of the transmission loss in an Example. 4 is a graph showing material constants of the formulation of Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductive reflection layer 2 Electromagnetic interference suppression body 3 Adhesion layer 54 Electromagnetic interference suppression sheet

Claims (11)

A sheet-like electromagnetic interference suppressor obtained by applying and drying a magnetic paint, containing 30 to 80% by volume of soft magnetic powder and 20 to 70% by volume of a binder, and storage elastic modulus at 20 to 60 ° C. (E ') is 10 < ⁹ > Pa or more (JIS K7244-1), The electromagnetic interference suppression body characterized by the above-mentioned. A sheet-like electromagnetic interference suppressor obtained by applying and drying a magnetic paint, comprising 30 to 80% by volume of soft magnetic powder and 20 to 70% by volume of a binder, the binder having a number average molecular weight (Mn) is Mn ≧ 1.5 × 10 ⁴ and is an elastomer or a resin having a storage elastic modulus (E ′) at 20 to 60 ° C. of 10 ⁷ Pa (JIS K 7244-1) or more. An electromagnetic interference suppressor.   The electromagnetic interference suppressor according to claim 1 or 2, wherein the sheet-like electromagnetic interference suppressor is manufactured without being substantially pressurized.   The electromagnetic interference suppressor according to any one of claims 1 to 3, wherein the binder is crosslinked.   The electromagnetic interference suppressor according to any one of claims 1 to 4, wherein 20 to 40 parts by weight of a crosslinking agent is blended with 100 parts by weight of the binder.   5. The real part (μ ′) of the complex relative permeability is 5 or more, or the imaginary part (μ ″) is 5 or more at frequencies of 100 MHz and 1 GHz, according to claim 1. Electromagnetic interference suppressor.   6. The electromagnetic interference suppressor according to claim 1, wherein an imaginary part (ε ″) of a complex relative dielectric constant is 500 or less at frequencies of 100 MHz and 1 GHz.   The electromagnetic interference suppressor according to any one of claims 1 to 6, wherein flame retardancy is imparted.   The electromagnetic interference suppressor according to claim 1, further comprising a pressure-sensitive adhesive layer or an adhesive layer on at least one surface.   A conductive reflective layer and the electromagnetic interference suppressor according to claim 1 provided on at least one surface of the conductive reflective layer, and obtained by a KEC method or an Advantest method at 10 MHz to 1 GHz. A magnetic shield sheet having a magnetic field shielding property of 10 dB or more.   An electromagnetic interference suppressing method comprising: disposing the electromagnetic interference suppressing body according to any one of claims 1 to 8 in or around an electronic device.

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