JPH11163579A - Electromagnetic wave leakage suppression sheet and electronic apparatus casing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve flexibility to avoid leakage of unwanted electromagnetic waves, including low- and high-frequency waves causing radio interference, by forming a sheet with a magnetic powder contg. magnetic particles of a specified size at a specified content. SOLUTION: To develop leakage-preventing effect of esp. unwanted low frequency electromagnetic waves, a magnetic powder contg. magnetic particles of 100 μm or more 50-100 wt.% among those substantially contained per unit vol. is preferable and a shape of amorphous magnetic powder having an anisotropy with an aspect ratio of 4 or less is preferable. An electromagnetic leakage suppression sheet 30 is provided adjacent to an opening 14 in a casing 10 as an antenna for electromagnetic waves generated from a circuit board or oscillation in the casing 10 and its spatial radiation pattern is changed to avoid leaking unwanted electromagnetic waves. The suppression sheet 30 is disposed partly or combined at several areas to absorb low frequency electromagnetic waves and avoid leakage of electromagnetic waves when used for electronics components.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic wave leakage suppression sheet which can effectively prevent leakage of unnecessary electromagnetic waves from a low frequency to a high frequency, and an electronic equipment housing using the same.

[0002]

2. Description of the Related Art A housing of an electronic device is generally made of a synthetic resin, a metal plate of aluminum or the like, or a composite material thereof, which is excellent in lightness and moldability. 2. Description of the Related Art Some internal circuits and electric components of electronic devices generate unwanted electromagnetic waves that cause radio interference such as noise and image distortion. In particular, many electronic devices equipped with integrated circuits, such as communication devices and information devices, handle high-frequency signals, and there is a high possibility that high-frequency leakage that causes radio interference will occur. In Japan, the United States, Europe, etc. where there are many opportunities to use,
Regulations on leakage of high-frequency electromagnetic waves have been tightened. In recent years, leakage of low-frequency electromagnetic waves has also been regarded as a problem, and prevention of leakage of low-frequency electromagnetic waves as well as high-frequency electromagnetic waves has been desired.

When the housing of an electronic device is made of synthetic resin,
Because synthetic resin has the property of transmitting electromagnetic waves well,
The leakage of the electromagnetic waves as described above becomes severe, and radio interference occurs. In order to prevent the leakage of electromagnetic waves, an attempt was made to use an electromagnetic wave shielding resin in which synthetic resin contains metal powder or the like having the property of shielding electromagnetic waves. However, the material cost is high and the performance of the synthetic resin such as moldability is reduced.

Therefore, it has been proposed to form a conductive layer made of metal plating or a conductive paint on the inner surface of a housing made of a usual electromagnetic wave transmitting synthetic resin. Since such a conductive layer has a property of reflecting electromagnetic waves,
Electromagnetic waves generated in the housing can be reflected so as not to leak outside the housing. FIG. 3 shows a schematic configuration of an electronic device housing having such a conventionally proposed electromagnetic wave shielding structure. Inside the synthetic resin case 10, a conductive layer 20 made of metal plating or conductive paint is formed, and the electromagnetic waves generated by the electromagnetic wave generation source 12 are reflected on the inner surface of the conductive layer 20, and It does not leak through the body 10 to the outside. Also, when the electronic device casing is formed of a thin metal plate such as aluminum, it is not necessary to provide a conductive layer that reflects electromagnetic waves,
Various measures have been taken to prevent the electromagnetic waves generated by the electromagnetic wave generation source from leaking to the outside.

[0005] As shown in FIG. 3, an electronic device housing usually has openings 1 such as a vent, an internal inspection port, and a signal cable port.
There are four. In the synthetic resin case and the metal case, the electromagnetic wave does not leak at the portion where the conductive layer 20 that reflects the electromagnetic wave is formed, and the electromagnetic wave is repeatedly reflected. This electromagnetic wave is highly likely to be generated inside the electronic device, and moreover, 0.3 to 3G, which is greatly affected by radio interference.
It is an electromagnetic wave in a frequency range of about Hz. Most of this electromagnetic wave energy easily passes through even a small opening or gap existing in the housing and goes to the outside, so it has been difficult to block such high-frequency electromagnetic wave leakage.

In addition, if a conductive layer is formed on the inner surface of the synthetic resin housing and the metal housing, the electromagnetic wave generated inside the housing is reflected by the conductive layer repeatedly, and the inner surface of the housing is repeatedly exposed. The whole will move and eventually leak intensively from the opening. In addition, the conductive layer acts as if it were a half-wavelength antenna and resonates, leading to secondary emission of electromagnetic waves from a local oscillator inside the housing. Therefore, the formation of the conductive layer is not an effective electromagnetic wave shielding means, and its improvement is demanded.

Japanese Patent Application Laid-Open No. Hei 6-97691 discloses that a housing and a substrate are made of a plate-like body having at least one surface made conductive, and a ferrite powder exhibiting a magnetic loss on the conductive surface of the plate-like body. There has been disclosed an electromagnetic wave shielding structure characterized by preventing unwanted leakage of an electromagnetic wave generated from an electronic circuit provided on a substrate stored in a housing by applying a thin film. However, since a paint containing a solvent is applied when a thin film is formed, it is necessary to perform masking in advance so that the paint does not adhere to portions where the thin film is unnecessary. In addition, if the housing is assembled with the board incorporating the electronic circuit,
Because of the dimensional shape, there is a problem that the coating containing such a solvent cannot be sufficiently applied, and that the control of the film thickness is difficult, and the effect cannot be obtained with good reproducibility. In addition, since the location where the paint is to be applied is not always sufficiently specified, leakage of an unwanted electromagnetic wave may be observed even after the application process.

[0008] In EP-A-0398672, 3
A magnetic sheet having a thickness of 75 μm to 37.5 mm for suppressing unnecessary radiation is disclosed. However, when these sheets are installed on the inner surface of the housing, since the thickness of the sheets is 375 μm to 37.5 mm, space saving is progressed due to downsizing and thinning of applied electronic devices, and mounting becomes difficult. ing.

In addition to the above, a method of incorporating a noise filter or a ferrite bead into the electronic circuit itself, a method of adding a magnetic material to a conductive shield to prevent leakage from a gap, and the like have been adopted. Significantly difficult to assemble, the effect is not sufficiently reproducible,
There have been problems such as the inability to sufficiently cope with the reduction in the size and size of the housing. When such a sheet is installed, 0 is set.
It is necessary that the sheet does not break even if it is bent such as T.

Therefore, the present inventors provide a sheet made of a magnetic material-containing resin composition comprising a binder resin and a magnetic powder having a magnetic loss term in a portion in contact with an opening of a housing or in the vicinity thereof. Proposed a method to reduce unnecessary radiation. In this technique, leakage of unnecessary high-frequency electromagnetic waves can be effectively prevented only by sticking a sheet to a part of the inside of the housing. However,
In some cases, the leakage of unnecessary low-frequency electromagnetic waves cannot be sufficiently prevented.

[0011]

SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to provide a highly flexible and effective prevention of leakage of unnecessary electromagnetic waves from a low frequency of 100 MHz or less to a high frequency which causes radio interference. It is an object of the present invention to provide an electromagnetic wave leakage suppression sheet and a housing of an electronic device using the same.

[0012]

According to the present invention, a particle size of 10
It is an electromagnetic wave leakage suppression sheet made of a magnetic powder containing 50 to 100% by weight of magnetic particles of 0 μm or more. Further, the present invention provides an electronic device in which the electromagnetic wave leakage suppression sheet is provided on at least a part selected from the group consisting of a surface of a housing, an inside of the housing, and a surface of cables connected to the housing. It is a device housing. Hereinafter, the present invention will be described in detail.

The electromagnetic wave leakage suppressing sheet of the present invention is made of a magnetic powder containing 50 to 100% by weight of magnetic particles having a particle diameter of 100 μm or more. The magnetic particles having a particle diameter of 100 μm or more exhibit magnetic loss with respect to electromagnetic waves from a low frequency such as 100 MHz or less to a high frequency such as 0.3 to 3 GHz.

[0014] Of the above magnetic particles, the particle diameter is 100 µm.
The content of the above magnetic particles is 50 to 1 in the above magnetic powder.
00% by weight. 5 having a particle diameter of 100 μm or more
When the content is less than 0% by weight, the effect of preventing the leakage of unnecessary low-frequency electromagnetic waves is small, so the content is limited to the above range.

There are various notations for expressing the state of the magnetic powder, but in the present invention, the content is specified by the content of magnetic particles having a particle diameter of 100 μm or more. When expressed by an average particle size such as area average or volume average, which is usually used to represent the state of the powder, since the value is easily affected by particles having a large particle size,
Even if the value of the average particle diameter is relatively large, the effect of preventing the leakage of unnecessary electromagnetic waves at a low frequency due to the magnetic particles having a large particle diameter cannot be obtained. That is, even if the average particle diameter is 100 μm or more, the amount of magnetic particles having a large particle diameter is 50% by weight.
If the ratio is less than the above range, the effect of preventing leakage of unnecessary low-frequency electromagnetic waves, which is the object of the present invention, cannot be obtained. In the case of a mixed powder composed of two kinds of powders having different particle diameter distributions or a powder having an irregular particle shape, the expression by the average particle diameter such as the area average or the volume average conventionally used is not used. It can easily be inferred that it does not make sense in expressing the state of the powder.

In the present invention, attention is paid only to the abundance of magnetic particles having a particle diameter of 100 μm or more among the magnetic particles substantially present in a unit volume. As long as the magnetic powder contains 50% by weight or more, the object of the present invention can be achieved, the magnetic particles having a particle diameter of less than 100 μm are not limited at all. That is, in order to exhibit the effect of preventing unnecessary leakage of low-frequency unnecessary electromagnetic waves, it is clear that the abundance of large-diameter magnetic particles that contribute to this performance is important.

Therefore, the particle size of the magnetic powder used in the present invention must be strictly measured, selected and provided for evaluation. The specified magnetic powder is significantly different from the conventional notation, for example, those having an average particle diameter of 100 μm or more.

The magnetic particles are not particularly limited as long as they exhibit magnetic loss, and examples thereof include a metal oxide magnetic material and a metal magnetic material. Above all,
Metal oxide magnetic materials are preferred. There are no particular restrictions regarding the metal oxide magnetic material, for example, MnO to Fe ₂ O _3,
ZnO, NiO, MgO, CuO, ferrite combining the Li ₂ O or the like; NiO-MnO-ZnO-Fe 2 O
_{3, MnO-ZnO-Fe 2} O 3, NiO-ZnO-F
spinel ferrites such as e ₂ O ₃ ; garnet type ferrites; spinel (cubic) γ-Fe ₂ O ₃ , γ-
Fe ₄ O _{4 and the} like can be mentioned. Among them, in the present invention, Li, Mg, Mn, Co, Ni, C
It is preferable to use an Fe oxide containing u, Sn, Sr, Ba and the like. These may be used alone,
More than one species may be used in combination.

The metal magnetic material is not particularly limited.
For example, a magnetic metal simple substance such as Fe, Co, and Ni; silicon steel;
Magnetic metal alloys such as Sendust, Supermalloy, Permalloy, and amorphous metals; Si, B, Al, Co, N
i, Cr, V, Sn, Zn, Pb, Mn, Mo, and Ag
And at least one Fe magnetic alloy containing at least one selected from the group consisting of: Among these, in the present invention, Si, B, Al, Co, Ni, Cr, V,
A Fe magnetic alloy containing at least one selected from the group consisting of Sn, Zn, Pb, Mn, Mo, and Ag;
A simple magnetic metal of Co or Ni is preferable. These may be used alone or in combination of two or more.

Of the above magnetic particles, the particle diameter is 100 μm
The above are, for example, the metal oxide magnetic material, a magnetic material block such as the metal magnetic material, pulverized using a stamp mill or the like, dry sieving method, air classification, wet sieving method, mechanical It can be obtained by classification using a wet classification method. The particle diameter obtained as described above is 1
The magnetic powder having a particle size of 00 μm or more
As a method for confirming that the particles are contained by weight, for example, when particles are sieved using a sieve having a mesh size of 100 μm, the amount of residual particles on the sieve falls within a range of 50 to 100% by weight. It can be determined by whether or not it is in.

The shape of the magnetic particles is not particularly limited, but is preferably irregular shaped particles in order to sufficiently exhibit the effect of preventing leakage of electromagnetic waves. In the present specification, the term “irregular shaped particles” mainly means particles having relatively little shape anisotropy, for example, particles having an aspect ratio of 7 or less, preferably 4 or less. In the present invention, a material having an aspect ratio larger than 7, such as a flat particle, a flaky particle, a needle particle, or a fibrous material, is not suitable as the magnetic particle. The reason for this is that flat particles and flaky particles are poorly compatible with the resin, and due to electromagnetic anisotropy, a sufficient effect of suppressing electromagnetic wave leakage cannot be obtained. This is because these materials have a very large anisotropy, so that the effect of suppressing electromagnetic wave leakage from low frequency to high frequency cannot be obtained.

The magnetic particles may be surface-treated with a silane coupling agent, a titanium-based coupling agent, an aluminate-based coupling agent, other additives, a resin, or the like, if necessary. By performing such a treatment, it is possible to introduce a functional group that imparts reactivity to the magnetic particles and a functional group that governs wettability. When the composite is formed as described above, magnetic particles subjected to a surface treatment are preferably used from the viewpoint of sheet productivity and film forming properties. The additives are not particularly limited, and include, for example, a surfactant, a wetting agent, and a viscosity reducing agent for improving the wettability and fluidity of the magnetic particles; a heat stabilizer for stability during production; Agents and the like.

The magnetic powder may be used as it is, but it may be difficult to form a sheet using the magnetic powder alone. Therefore, the magnetic powder may be used as a composite material comprising the magnetic powder and a binder. Is preferred. As the binder, a thermosetting resin and a thermoplastic resin can be used, and among them, a thermoplastic resin is preferable. The thermoplastic resin is not particularly limited, and examples thereof include non-polar resins such as polyethylene, polypropylene, polymethylpentene, polybutene, crystalline polybutadiene, polystyrene, polybutadiene, and styrene butadiene; polyvinyl chloride, polyvinyl acetate, and polymethyl methacrylate. , Polyvinylidene chloride, polytetrachloroethylene, ethylene-vinyl acetate copolymer (EVA), modified ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-vinyl chloride graft copolymer resin, chlorinated polyethylene resin, styrene-acrylonitrile copolymer Polymer resin (SAN resin), acrylonitrile-butadiene-styrene copolymer resin (ABS resin), acrylate-styrene-acrylonitrile copolymer resin (ASA resin), chlorinated polyethylene-acryl Nitrile-styrene copolymer resin (ACS resin), polyacetal resin, polyamide resin, polycarbonate resin, polyphenylene ether resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polyacrylate resin, polysulfone resin, polyimide resin, polyamideimide resin, polyphenylene sulfide Resins such as resins, polyoxybenzoyl resins, polyetheretherketone resins, polyetherimide resins, silicone resins, and epoxy resins; and modified resins thereof. These may be used alone,
More than one species may be used in combination.

As the binder, the wettability with the magnetic particles, the viscosity at the time of kneading the resin, the temperature, the physical properties of the film, the chemical resistance, the heat resistance, the water resistance, the adhesiveness to metals and plastics, etc. It can be appropriately selected in consideration of the above. Among them, ethylene-vinyl acetate copolymer, modified ethylene-
A resin selected from vinyl acetate copolymer, ethylene-vinyl acetate-vinyl chloride graft copolymer, chlorinated polyethylene resin, vinyl chloride resin, polyester resin, acrylic resin, amide resin, silicone resin, epoxy resin,
And these modified resins are preferable.

Preferably, the binder is added in an amount of 4 to 100 parts by weight based on 100 parts by weight of the magnetic powder. If the amount is less than 4 parts by weight, the productivity of the sheet is not sufficient, and if it exceeds 100 parts by weight, it is not possible to sufficiently suppress the leakage of low-frequency unnecessary electromagnetic waves.

The electromagnetic wave leakage suppressing sheet of the present invention can be manufactured, for example, by the following method. Using a roll, a Banbury mixer, a pressure kneader, or the like, kneading the surface-treated magnetic powder, a binder and other additives as necessary to obtain a magnetic material-containing resin composition, and further applying a pressure press, a calender The sheet is formed by a roll, an extruder, or the like. When using a resin plasticized with a plasticizer, such as a vinyl chloride resin, or a resin dissolved or dispersed as necessary with an organic solvent or water, a solution or paste containing a magnetic substance powder is known. The sheet can also be formed by coating with a coating machine of No. 1 and removing volatile components.

If necessary, a resin dissolved in an organic solvent or water or a resin in the form of a dispersion is used as a binder, applied to a film serving as a base material, and a magnetic powder is applied thereon by utilizing electrostatic force. Alternatively, the sheet can be formed by arranging the sheet uniformly by mechanical force, and thereafter, if necessary, further applying a resin component or the like, and then removing volatile components. In this case, since the magnetic powder and the binder are not uniformly mixed, the amount of the binder used is
Although the same description as a homogeneous mixture composition can not be made,
In general, about 5 to 20 parts by weight of a binder is required for fixing the magnetic powder to 100 parts by weight of the magnetic powder.

Further, if necessary, a resin dissolved in an organic solvent or water or a resin in the form of a dispersion is used as a binder, applied to a film serving as a base material, and the resin applied layer is dried to form an adhesive layer. Thereafter, the magnetic powder is uniformly arranged on the adhesive layer by using an electrostatic force or a mechanical force, and then, if necessary, after further applying a resin component, etc., to remove volatile components. By removing the sheet, the sheet can be formed. In this case, since the magnetic powder and the binder are not uniformly mixed, the amount of the binder used cannot be described in the same manner as in the homogeneous mixture composition. About 5 to 20 parts by weight of the binder is required for fixing the magnetic powder.

When the above binder is not used,
The magnetic powder can be made into a sheet by holding it on a film or an adhesive material. The magnetic powder has a particle diameter of 1
Since it contains a large number of large particles of not less than 00 μm, the shape can be stably maintained by using the film or the adhesive. The material of the film is not particularly limited. For example, polypropylene, polyethylene, polyamide, polyurethane, polyvinyl alcohol, polybutadiene, polybutene, silicone resin; plasticized polyvinyl chloride, polyurethane plasticized polyvinyl chloride, plasticized (vinyl acetate) -Vinyl chloride resins such as (vinyl chloride copolymer); those having alkyl (meth) acrylate as a base polymer; cloth; paper;

The pressure-sensitive adhesive is not particularly limited, and may be a pressure-sensitive adhesive layer alone or may have a pressure-sensitive adhesive layer on both sides of a support. The pressure-sensitive adhesive layer is not particularly limited, and includes, for example, rubber-based pressure-sensitive adhesives such as styrene-isoprene-styrene block copolymer, styrene-butadiene rubber, polybutene, polyisoprene, butyl rubber, and natural rubber; ethyl (meth) acrylate; An acrylic adhesive such as an alkyl (meth) acrylate such as propyl (meth) acrylate; an epoxy adhesive; a urethane adhesive; a silicone adhesive; The support is not particularly limited, and examples thereof include those exemplified as the material of the above-described film.

When the above-mentioned pressure-sensitive adhesive is used, the pressure-sensitive adhesive layer on one side of the pressure-sensitive adhesive is preferably protected by release paper. By using an adhesive whose one surface is protected by release paper, one adhesive surface can be protected by release paper during sheet production. Further, when the electromagnetic wave leakage suppression sheet is installed on an electronic device housing, a circuit board, or the like, the sheet can be adhered only by peeling off the release paper from the adhesive layer without using an adhesive or the like.

When the electromagnetic wave leakage suppressing sheet of the present invention is such that the magnetic powder is held on the film or the adhesive, the film or the adhesive is further laminated on the layer of the magnetic powder. Preferably, it is By sandwiching both surfaces of the magnetic powder layer with a sheet or an adhesive, the magnetic powder layer can be protected, and the shape can be more stably maintained. The film and the pressure-sensitive adhesive are not particularly limited, and include those described above.

The thickness of the electromagnetic wave leakage suppressing sheet obtained as described above is preferably 0.15 to 20 mm. If the thickness is less than 0.15 mm, leakage of unnecessary electromagnetic waves cannot be sufficiently prevented, and if it exceeds 20 mm, there is no problem with the effect on unnecessary electromagnetic wave leakage. Location restrictions are increased, the range of use is limited, installation according to the housing shape becomes difficult, and uniformity during sheet production is impaired. Preferably, it is 0.2 to 10 mm.

In the electromagnetic wave leakage suppression sheet of the present invention, the content of the magnetic powder in the sheet is preferably 15 to 81% by volume per unit volume. 15% by volume
If the amount is less than the above, the effect of suppressing unnecessary electromagnetic wave leakage is small, and if it exceeds 81% by volume, the flexibility becomes insufficient.

The sheet for suppressing electromagnetic wave leakage of the present invention is excellent in flexibility, so that it can be installed regardless of whether the installation location is flat or curved. If the installation surface is very small, such as a cable or a cord, it can be wound.

Further, the electromagnetic wave leakage suppression sheet of the present invention comprises:
Since it can be easily cut using scissors, etc., it is not necessary to process the sheet into a shape suitable for the installation location in advance when manufacturing the sheet. Can be.

The sheet for suppressing electromagnetic wave leakage according to the present invention can effectively suppress the leakage of low-frequency electromagnetic waves and has excellent flexibility, so that it is used for electronic equipment such as housings, cables, cords, and the like. The present invention can be suitably used for components that need to prevent leakage of electromagnetic waves, such as a housing, a cable, and a cord.

The electronic device housing according to the present invention includes the above-described electromagnetic wave leakage suppressing sheet according to the present invention, which is provided on the surface of the housing, inside the housing,
And it is provided on at least a part of the surface of cables connected from the housing. In the present specification, the “electronic device housing” refers not only to the housing itself containing the integrated circuit and the like, but also to an integrated circuit built in the housing, a device connected to a circuit board, and the like to a device outside the housing. It also means accessories that are directly connected to the housing, such as cables for connection.

The housing is usually made of synthetic resin, wood material,
It is formed of an electromagnetic wave transmitting material such as an inorganic material, and has a conductive layer on an inner surface thereof. As the synthetic resin, an ordinary molding resin can be used.

As the conductive layer formed on the inner surface of the housing, a normal electromagnetic wave reflecting material used in the conventionally proposed electromagnetic wave shielding structure is used, and the conductive layer is formed on the inner surface of the housing. As for the method described above, an ordinary method can be adopted. For example, plating the inner surface of the housing with a conductive metal such as copper or aluminum, forming these metals into a thin film by a method such as vapor deposition, attaching them to a metal foil, and applying a metal powder to the paint. Examples thereof include a method of applying various conductive paints obtained by mixing, a method of attaching a film made of a conductive resin using an adhesive or a pressure-sensitive adhesive, and the like. The thickness of the conductive layer varies depending on the type and amount of electromagnetic waves generated in the housing and the combination with the electromagnetic wave absorbing layer, but is usually preferably 40 to 60 μm. As the shape and structure of the housing, any shape and structure suitable for the entire structure of the electronic device can be adopted. Further, due to the function of the electronic device, an opening such as a slit, a hole, or a notch may be present in at least a part of the housing.

The opening of the housing is provided for inputting and outputting signals, current, power, and other optical and physical energies necessary for the electronic device to operate. A display device for displaying image information by lines, liquid crystals, LEDs, etc .; an operation display device; a receiving device for a remote control;
Terminal device; Battery power supply device; Speaker device; Sound transmission port and sound output port of mobile phone etc .; CD, CD-RO
A device that is in contact with the inside of the housing, such as a drive for M, floppy, cassette tape, disk, mini disk, etc .;
An opening provided for the purpose of cooling the inside of the housing; a portion that is open to the inside and outside of the housing, such as a joint caused by molding of the housing such as a joint or a joint of the housing.

The place where the electromagnetic wave leakage suppression sheet is installed is not particularly limited, and the inner surface of the housing,
The outer surface of the housing, the portion in contact with the opening of the housing or in the vicinity thereof, between the circuit boards provided in the housing, the upper surface of the integrated circuit mounted on the housing, and the cables connected from the housing. Any surface or the like may be used. The location where electromagnetic waves leak
Since it depends on the shape and size of the housing and other factors,
It is preferable that the above-mentioned electromagnetic wave leakage suppression sheet is installed at a necessary place corresponding to a part where the electromagnetic wave is leaking for each housing. When the electromagnetic wave leakage suppression sheet is provided on the inner surface of the housing, it is preferable to provide an insulating layer on the conductive layer. In addition, if the electromagnetic wave leakage suppression sheet is installed on the entire inner surface of the housing, adverse effects such as resonance may be caused. Therefore, it is preferable to install the sheet at a specific location.

As a method for selecting a place where the electromagnetic wave leakage suppression sheet is installed, for example, the following method can be mentioned. First, an arbitrary measurement reference point is provided on the housing, and measurement locations are sequentially changed from the reference point to confirm a location where electromagnetic waves are leaking. The measurement of the electromagnetic wave is performed using a loop antenna, a noise scanner, or the like. When an electromagnetic wave leakage location is specified, the electromagnetic wave leakage suppression sheet is installed according to the location. For example, if the cause of unnecessary electromagnetic wave leakage is in the housing itself, leakage from an opening or a gap, a resonance phenomenon due to the size of the housing can be considered, but in the former case, around the opening, and in the latter case, In the case of (1), by installing the electromagnetic wave leakage suppression sheet on a part of the inner surface of the housing, it is possible to obtain effects on leakage and resonance as well as magnetic loss. If the cause of unnecessary electromagnetic wave leakage is a circuit board, leakage from components, leakage from printed wiring on the board, leakage from wiring, etc. are considered. By installing the above, a magnetic loss and a shielding effect can be obtained. If the cause of the unnecessary electromagnetic wave leakage is caused by cables outside the housing, the effect of magnetic loss can be obtained by winding or attaching the electromagnetic wave leakage suppression sheet around the cable or the power cord.

Further, when the electromagnetic wave leakage suppression sheet is installed in the inside of a housing or a specific place of cables, even if the installation area of the sheet is very small, unnecessary electromagnetic wave leakage can be prevented in a low frequency region. The effect may appear dramatically. Therefore, by finding the location, the amount of use of the electromagnetic wave leakage suppression sheet can be reduced.

The method of installing the electromagnetic wave leakage suppression sheet is not particularly limited. For example, a double-sided tape may be placed on the inner surface of the casing obtained by applying a conductive treatment to the sheet.
A method of sticking with an adhesive or the like; a method of integrating the sheet with the housing by a high-frequency sewing machine, hot press, or the like; a method of attaching the sheet to the housing and fixing it with tape, another film, panel, jig, or the like from above. And the like. When the electromagnetic wave leakage suppression sheet has an adhesive layer, the sheet can also be installed by attaching an adhesive surface to a housing. When the installation location is a cable or a cord connected directly from the circuit board even inside the housing, the electromagnetic wave leakage suppression sheet may be wound.

An electronic equipment housing according to the present invention includes an automobile telephone,
Communication devices such as mobile phones, PHS phones, wireless LAN terminals, adapters, POS terminals, etc .; players such as personal computers, word processors, DVDs, etc .; home appliances such as game machines, small radios, televisions, etc .; DCCs; cassette recorders; It can be used for devices and the like that generate and use.

In order to prevent unnecessary leakage of electromagnetic waves, the electronic device housing of the present invention is used as an electromagnetic wave leakage suppression sheet installed on the surface of the housing, inside the housing, cables, etc., having a particle diameter of 100 μm or more. Because it uses a large amount of large magnetic particles, it effectively prevents the leakage of low-frequency electromagnetic waves that could not be prevented when using conventional electromagnetic wave shielding materials etc. be able to.

The use of the electromagnetic wave leakage suppression sheet suppresses the leakage of electromagnetic waves due to the shielding effect of the electromagnetic wave leakage suppression sheet; By changing the spatial radiation pattern of the generated radio waves,
An effect of preventing leakage from the opening; a magnetic loss effect and the like can be considered.

[0049]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.

FIG. 1 shows an embodiment of an electronic apparatus housing according to the present invention. (A) shows that the electromagnetic wave leakage suppression sheet 30 is
It is provided at a portion in contact with the opening portion 14 in the inside of the housing. At this time, the electromagnetic wave leakage suppression sheet 30 serves as an antenna for electromagnetic waves generated from the circuit board 11 and electromagnetic waves generated by resonance in the housing 10, and prevents leakage of unnecessary electromagnetic waves by changing the spatial radiation pattern of the electromagnetic waves. .

(B) shows that the electromagnetic wave leakage suppression sheet 30 is
It is provided on the inner surface of the housing 10. In (c), the electromagnetic wave leakage suppression sheet 30 is provided in parallel between the circuit boards 11. The distance between the electromagnetic wave leakage suppression sheet 30 and the circuit board 11 is 0.2 mm or more. In (d), the electromagnetic wave leakage suppression sheet 30 is provided on the upper surface of the integrated circuit 13 mounted inside the housing 10. (B)-(d)
In the case of (1), the electromagnetic wave leakage suppression sheet 30 shields the electromagnetic wave and prevents leakage of the electromagnetic wave.

The electromagnetic wave leakage suppressing sheet 30 includes (a)
It may be installed only in a part like (d), (a)-
A plurality of locations may be installed by combining (d). In addition, it may be appropriately installed according to a place where the electromagnetic wave leaks from the housing 10.

FIG. 2 shows an embodiment in which the electromagnetic wave leakage suppression sheet 30 is installed on cables connected from the housing 10. (E) is an installation method in the case of a round cable, in which the electromagnetic wave leakage suppression sheet 30 is wound around the cable 41. (F) is an installation method in the case of a flat cable, in which the electromagnetic wave leakage suppression sheet 30 is installed on the plane of the cable 42.

[0054]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Production Example 1 A block of a Ni—Zn ferrite sintered body was roughly pulverized by a stamp mill and further pulverized by a pin mill to obtain a ferrite powder (1) having a wide particle size distribution. Production Example 2 106 μm of the ferrite powder (1) obtained in Production Example 1
The particle size distribution is 106 to 300 μm using three types of sieves: mesh, 300 μm mesh and 600 μm mesh.
Ferrite powder (2) having a particle size distribution of 300 to
A ferrite powder (3) having a size of 600 μm was obtained. The ferrite powder (2) and the ferrite powder (3) thus obtained have a particle diameter of 100 μm or more for both powders by measuring the amount of residual particles when using a 100 μm mesh sieve. Was confirmed to be 100% by weight.

Comparative Production Example 1 The ferrite powder (1) obtained in Production Example 1 was subjected to airflow classification to have a particle size distribution of 1 to 50 μm (77% of the total volume is 16 μm or less in particle size, 50 μm in maximum particle size). Was obtained as ferrite powder (4). The ferrite powder (4) thus obtained was measured for the amount of residual particles using a sieve having a mesh size of 100 μm to obtain a powder (100 μm or more) containing no particles having a particle size of 100 μm or more. (The content of the particles was 0% by weight).

Example 1 A ferrite powder (2) having a particle size distribution of 106 to 300 μm was blended in an ethylene-vinyl acetate copolymer (EVA) so that the ferrite powder (2) became 90% by weight. And kneaded with a roller mixer to obtain a kneaded body (A) of ferrite powder (2) and resin. In the obtained kneaded body (A), the content volume of the ferrite powder (2) was 61.
8% by volume. The complex relative permeability of the kneaded body (A) is measured, and the maximum value of the imaginary part μr ″ of the complex relative permeability and the frequency at that time, and the frequency (ratio where the real part μr ′ and the imaginary part μr ″ are equal) Table 1 shows the magnetic permeability (frequency when tan δ = 1).

Measurement of Complex Permeability The material to be measured was processed into a ring core shape having an inner diameter of 3.04 mm, an outer diameter of 7.00 mm, and a thickness of 3.0 mm, and a network analyzer manufactured by Hewlett-Packard Company (HP8510).
B) and material constant measurement software (HP85071)
Using B), a coaxial tube having an inner diameter of 7 mm is filled with a material to be measured processed into a ring core shape, and a frequency of 100 MHz to
A complex relative magnetic permeability of 18 GHz was measured. Calibration of the device
Performed by TRL-full two-port calibration.

Example 2 Ferrite powder (3) having a particle size distribution of 300 to 600 μm was mixed with 90% by weight of ferrite powder (3) in EVA.
The kneaded product (B) was obtained in the same manner as in Example 1. In the obtained kneaded body (B), the content volume of the ferrite powder (3) was 61.8% by volume. The complex relative permeability of the kneaded body (B) was measured in the same manner as in Example 1. The maximum value of the imaginary term μr ″ and the frequency at that time, and the real term μr ′ and the imaginary term μr ″ of the complex relative permeability were measured. Are shown in Table 1 (frequency when tan δ = 1 with respect to relative magnetic permeability).

Example 3 A ferrite powder (2) having a particle size distribution of 106 to 300 μm and a ferrite powder (4) having a particle size distribution of 1 to 50 μm were mixed at a volume ratio of 50:50. The ferrite powder (5) thus obtained was blended in EVA so that the ferrite powder (5) became 90% by weight, and a kneaded body (C) was obtained in the same manner as in Example 1. The obtained kneaded body (C)
Had a content volume of ferrite powder (5) of 61.8% by volume. The ferrite powder (5) was confirmed to contain 50% by weight of particles having a particle diameter of 100 μm or more by measuring the residual particle amount of the sieve using a 100 μm mesh sieve. The complex relative permeability of the kneaded body (C) was measured in the same manner as in Example 1, and the maximum value of the imaginary part μr ″ and the frequency at that time, and the real part μr ′ and the imaginary part μr ″ of the complex relative permeability were measured. Are shown in Table 1 (frequency when tan δ = 1 with respect to relative magnetic permeability).

Comparative Example 1 Ferrite powder having a particle size distribution of 1 to 50 μm (4)
Was mixed with EVA so that the ferrite powder (4) was 90% by weight, and a kneaded body (D) was obtained in the same manner as in Example 1. In the obtained kneaded body (D), the content volume of the ferrite powder (4) was 61.8% by volume. The complex relative permeability of the kneaded body (D) was measured in the same manner as in Example 1, and the maximum value of the imaginary term μr ″ of the complex relative permeability and the frequency at that time, and the real term μr ′ and the imaginary term μr ″ Are shown in Table 1 (frequency when tan δ = 1 with respect to relative magnetic permeability).

Comparative Example 2 Ferrite powder (2) having a particle size distribution of 106 to 300 μm and ferrite powder (4) having a particle size distribution of 1 to 50 μm were mixed at a volume ratio of 45:55. The ferrite powder (6) thus obtained was blended in EVA so that the ferrite powder (6) became 90% by weight, and a kneaded body (E) was obtained in the same manner as in Example 1. The obtained kneaded body (E)
Had a content volume of ferrite powder (6) of 61.8% by volume. The ferrite powder (6) was confirmed to contain 45% by weight of particles having a particle size of 100 μm or more by measuring the residual particle amount of the sieve using a 100 μm mesh sieve. The complex relative permeability of the kneaded body (E) was measured in the same manner as in Example 1, and the maximum value of the imaginary term μr ″ and the frequency at that time, and the real term μr ′ and the imaginary term μr ″ of the complex relative permeability were measured. Are shown in Table 1 (frequency when tan δ = 1 with respect to relative magnetic permeability).

[0063]

[Table 1]

Example 4 The kneaded product (A) obtained in Example 1 was laminated on an adhesive (material of the adhesive layer: acrylic adhesive) to form a sheet having a thickness of 500 μm. The obtained sheet was folded in two and bent to check its flexibility. However, the sheet had sufficient flexibility, and no cracks or cracks were observed. The obtained sheet was cut into a size of 1 cm × 15 cm, and affixed near the opening of the electronic device housing. When the intensity of unnecessary radiation was measured by a method based on the 3 m method in a simple anechoic chamber, it was 32 dBμV / m at 288 MHz.

Example 5 Except that the kneaded product (B) obtained in Example 2 was used,
A sheet having a thickness of 500 μm was formed in the same manner as in Example 4. The obtained sheet was folded in two and bent to check its flexibility. However, the sheet had sufficient flexibility, and no cracks or cracks were observed. The obtained sheet was attached near the opening of the electronic device housing in the same manner as in Example 4. The intensity of the unwanted radiation was measured in the same manner as in Example 4.
It was 30 dBμV / m at 88 MHz.

Example 6 Except that the kneaded product (C) obtained in Example 3 was used,
A sheet having a thickness of 500 μm was formed in the same manner as in Example 4. The obtained sheet was folded in two and bent to check its flexibility. However, the sheet had sufficient flexibility, and no cracks or cracks were observed. The obtained sheet was attached near the opening of the electronic device housing in the same manner as in Example 4. The intensity of the unwanted radiation was measured in the same manner as in Example 4.
It was 33 dBV / m at 88 MHz.

Comparative Example 3 Except for using the kneaded product (D) obtained in Comparative Example 1,
A sheet having a thickness of 500 μm was formed in the same manner as in Example 4. The obtained sheet was attached near the opening of the electronic device housing in the same manner as in Example 4. When the intensity of the unnecessary radiation wave was measured in the same manner as in Example 4, the intensity was 47 d at 288 MHz.
BμV / m.

Comparative Example 4 Except that the kneaded product (E) obtained in Comparative Example 2 was used,
A sheet having a thickness of 500 μm was formed in the same manner as in Example 4. The obtained sheet was attached near the opening of the electronic device housing in the same manner as in Example 4. When the intensity of the unnecessary radiation wave was measured in the same manner as in Example 4, it was 45 d at 288 MHz.
BV / m.

From the above, when a sheet formed by using a ferrite powder containing a large amount of ferrite particles having a large particle diameter is used, it is possible to absorb lower-frequency electromagnetic waves, and to provide a housing for an electronic device. It has been found that when installed, it is possible to suppress leakage of low-frequency electromagnetic waves.

[0070]

Since the electromagnetic wave leakage suppressing sheet of the present invention has the above-described structure, it can absorb low-frequency electromagnetic waves which could not be sufficiently absorbed by the conventional electromagnetic wave shielding material. By applying to components, leakage of electromagnetic waves can be sufficiently suppressed. Further, since the electromagnetic wave leakage suppression sheet of the present invention has excellent flexibility, the place where the sheet is installed is not limited, and the sheet can be used by winding it around a curved surface such as a cable or a cord.

Since the electronic device housing of the present invention is provided with the electromagnetic wave leakage suppressing sheet of the present invention at least in a part thereof,
Leakage of unnecessary electromagnetic waves generated from low frequency to high frequency generated inside the housing and unnecessary radiation generated by resonance can be effectively prevented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of a housing of an electronic device housing according to the present invention.

FIG. 2 is a schematic diagram showing a cable section of an electronic device housing of the present invention.

FIG. 3 is a cross-sectional view schematically illustrating an example of a conventional electronic device housing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Case 11 Circuit board 12 Electromagnetic wave generation source 13 Integrated circuit 14 Opening 20 Conductive layer 30 Electromagnetic wave leakage suppression sheet 41 Round cable 42 Flat cable

Claims (12)

[Claims] A magnetic particle having a particle diameter of 100 μm or more
An electromagnetic wave leakage suppression sheet comprising a magnetic powder containing 0 to 100% by weight. 2. The electromagnetic wave leakage suppression sheet according to claim 1, wherein the magnetic particles are a metal oxide magnetic material. 3. The magnetic particles include Li, Mg, Mn, Co,
The sheet for suppressing electromagnetic wave leakage according to claim 2, wherein the sheet is an Fe oxide containing at least one selected from the group consisting of Ni, Cu, Sn, Sr, and Ba. 4. The magnetic particle according to claim 1, wherein the magnetic particle is a metal magnetic material.
The electromagnetic wave leakage suppression sheet as described in the above. 5. The magnetic particles include Si, B, Al, Co, and N.
i, Cr, V, Sn, Zn, Pb, Mn, Mo, and Ag
The sheet for suppressing electromagnetic wave leakage according to claim 4, wherein the sheet is an Fe magnetic alloy containing at least one selected from the group consisting of: or a magnetic metal simple substance of Fe, Co, or Ni. 6. The electromagnetic wave leakage suppressing sheet according to claim 1, wherein the magnetic particles are irregular shaped particles. 7. The magnetic powder according to claim 1, 2, 3, 4, 5, or 6 used as a composite material with a binder.
The electromagnetic wave leakage suppression sheet as described in the above. 8. The electromagnetic wave leakage suppression sheet has a thickness of 0.1%.
The electromagnetic wave leakage suppressing sheet according to claim 1, which is 5 to 20 mm. 9. The method according to claim 1, wherein the volume content of the magnetic powder is 15 to 81% by volume per unit volume.
9. The electromagnetic wave leakage suppression sheet according to 6, 7, or 8. 10. The electromagnetic wave leakage suppression sheet according to claim 1, wherein the magnetic powder is held on a film or an adhesive material. Leak control sheet. 11. The electromagnetic wave leakage suppressing sheet according to claim 10, further comprising a film or an adhesive laminated on the magnetic powder. 12. The electromagnetic wave leakage suppression sheet according to claim 1, which is selected from the group consisting of a surface of a housing, an inside of the housing, and a surface of cables connected to the housing. An electronic device housing provided at least in part.