JP2017183675A - Electromagnetic wave shielding enclosure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic wave shielding enclosure capable of being manufactured by insert molding and in-mold molding utilizing pressure forming and vacuum forming, suppressing a metal layer from being broken, and excellent in bond strength between a shielding material and the enclosure.SOLUTION: An electromagnetic wave shielding enclosure includes a resin-made enclosure body and an electromagnetic wave shielding material for bonding and coating the inner surface and/or the outer surface of the resin-made enclosure body. The electromagnetic wave shielding material has a multilayer structure where at least one sheet of metal foil and at least one sheet of resin film are laminated in close contact with each other. A layer of the electromagnetic wave shielding material forming a joint surface with the inner surface and/or the outer surface of the resin-made enclosure body is formed of a resin film.SELECTED DRAWING: Figure 1-1

Description

  The present invention relates to an electromagnetic wave shielding casing. More specifically, the present invention relates to a housing for accommodating an electric / electronic device therein to block electromagnetic waves radiated from the electric / electronic device.

  In recent years, interest in global environmental issues has increased worldwide, and the spread of environmentally friendly vehicles equipped with secondary batteries such as electric vehicles and hybrid vehicles is progressing. Many of these automobiles employ a method of obtaining a driving force by converting a direct current generated from a mounted secondary battery into an alternating current through an inverter and then supplying necessary power to the alternating current motor. Electromagnetic waves are generated due to the switching operation of the inverter. Since electromagnetic waves interfere with the reception of in-vehicle acoustic devices and wireless devices, measures have been taken to shield the electromagnetic waves by housing a battery, a motor or the like together with an inverter or an inverter in a metal case (Japanese Patent Laid-Open No. 2003). -285002).

  Moreover, electromagnetic waves are radiated not only from automobiles but also from many electric / electronic devices including communication devices, displays and medical devices. Electromagnetic waves can cause malfunction of precision equipment, and there is also concern about the effects on the human body. For this reason, various techniques for reducing the influence of electromagnetic waves using electromagnetic shielding materials have been developed. For example, a copper foil composite formed by laminating a copper foil and a resin film is used as an electromagnetic shielding material (Japanese Patent Laid-Open No. 7-290449). The copper foil has electromagnetic shielding properties, and the resin film is laminated for reinforcing the copper foil. There is also known an electromagnetic wave shield structure in which metal layers are laminated on the inner side and the outer side of an intermediate layer made of an insulating material (Japanese Patent No. 4602680).

  On the other hand, film insert molding and in-mold molding are known as methods for integrally molding a resin material and a metallic shield material. In JP-A-4-135815, the shield material and the resin are integrally formed by film insert molding. As the shielding material, in addition to the metal foil, a material obtained by laminating a polymer film on the surface of the metal foil is described. Japanese Patent Application Laid-Open No. 6-29669 describes that a housing for electronic equipment is manufactured by integrally molding a base such as aluminum and a synthetic resin by in-mold molding. Japanese Patent Laid-Open No. 6-29669 considers the thinning of the housing, and the thickness of the synthetic resin component that can be molded is 0.8 mm or more, and the thickness of the base must be 0.3 mm or more for strength calculation. It is described that. In any of the above publications, after the shield material is pressed and primary molded, secondary molding that integrates with the resin is performed.

JP 2003-285002 A JP 7-290449 A Japanese Patent No. 4602680 JP-A-4-135815 JP-A-6-29669

  In order to achieve both excellent electromagnetic shielding effect and moldability, the thickness of the metal layer constituting the shield material should be increased. However, the strength of the metal layer is increased, and the pre-stage of insert molding or in-mold molding is increased. At the stage of foam molding, pressure molding or vacuum molding cannot be adopted, and press molding is required. Japanese Patent Application Laid-Open Nos. 4-135815 and 6-29669 also employ press molding. However, unlike pressure forming and vacuum forming, which can be formed only with the upper or lower mold, press molding requires upper and lower molds, and the clearance between the upper and lower molds is also important, so accuracy is also required and high cost. It is. Therefore, it is not suitable for manufacturing a wide variety of products, and it is disadvantageous in that it cannot cope with products whose design is changed in a short span.

  On the other hand, in automobiles, weight reduction is a major issue from the viewpoint of improving fuel consumption, and studies are also underway on switching from metal materials to resin materials and carbon fiber materials. However, the resin material and the carbon fiber material cannot be expected to have an electromagnetic wave shielding effect. However, if the thickness of the metal layer is too small, an excellent shielding effect (for example, 36 dB or more at 1 MHz to 1000 MHz) cannot be obtained, and the thin metal layer is not ductile, so it cannot withstand forming and breaks. Resulting in.

  In this regard, the techniques described in JP-A-7-290449 and Japanese Patent No. 4602680 aim at a shielding effect with a composite of an insulating layer and a metal layer, and although a certain amount of weight can be reduced, In these publications, there is a lack of consideration regarding the joining of the shielding material and the casing made of the composite of the insulating layer and the metal layer. In particular, how to make an electromagnetic shielding case where the shield material and the case are bonded with excellent bonding strength by insert molding or in-mold forming using pressure forming or vacuum forming, and the metal layer breakage is suppressed during molding. There is no description or suggestion as to whether to manufacture. If the electromagnetic shielding material is peeled off from the housing, the shielding characteristics may be adversely affected, and the aesthetics will be impaired.

  The present invention has been created in view of the above circumstances, and can be manufactured by insert molding or in-mold molding using compressed air molding or vacuum molding, the metal layer is prevented from being broken, and a shielding material and a casing Another object is to provide an electromagnetic wave shielding casing having excellent bonding strength.

  The present inventor has made extensive studies to solve the above problems, and when the metal foil and the resin film are adhered and laminated, the metal foil easily follows the resin film and is easily stretched. It was found to be suppressed. Further, the outermost layer of the electromagnetic shielding material having a multilayer structure of metal foil and resin film is formed of a resin film, and the resin film is bonded to the resin casing, thereby increasing the bonding strength with the casing. I found out. The present invention has been completed based on this finding.

  In the first aspect, the present invention is an electromagnetic wave shielding case comprising a resin case main body and an electromagnetic wave shielding material that covers and covers the inner surface and / or the outer surface of the resin case main body. The layer of the electromagnetic shielding material having a multilayer structure in which at least one metal foil and at least one resin film are closely laminated, and forming a joint surface with the inner surface and / or outer surface of the resin casing body is a resin. It is an electromagnetic wave shielding housing composed of a film.

  In one embodiment of the electromagnetic wave shielding casing according to the first aspect of the present invention, the metal foil and the resin film constituting the electromagnetic wave shielding material are adhered and laminated by thermocompression bonding.

  In another embodiment of the electromagnetic wave shielding casing according to the first aspect of the present invention, the layer of the electromagnetic shielding material forming the bonding surface with the inner surface and / or the outer surface of the resin casing main body is formed of the resin casing. It is comprised with the resin film which consists of the same kind of resin material as a main body.

  In still another embodiment, the electromagnetic wave shielding casing according to the first aspect of the present invention is a resin film that is a layer of an electromagnetic shielding material that forms a bonding surface with the inner surface and / or the outer surface of the resin casing main body. The melting point of the constituent resin is within ± 5 ° C. with respect to the melting point of the resin constituting the resin casing body.

  In still another embodiment of the electromagnetic wave shielding casing according to the first aspect of the present invention, there is no broken portion of the metal foil and the resin film constituting the electromagnetic wave shielding material.

  In still another embodiment of the electromagnetic wave shielding casing according to the first aspect of the present invention, the electromagnetic wave shielding material has a structure in which at least two metal foils are laminated via a resin film.

In another embodiment of the electromagnetic wave shielding casing according to the first aspect of the present invention, all combinations of the metal foil and the resin film constituting the electromagnetic wave shielding material are σ _M × d _M × d _R ≧ 3 ×. ^10-3 is satisfied.
However, the symbol in a formula shows the following.
σ _M : conductivity of metal foil at 20 ° C. (S / m)
d _M : Metal foil thickness (m)
d _R : thickness of resin film (m)

In still another embodiment of the electromagnetic wave shielding casing according to the first aspect of the present invention, the electrical conductivity at 20 ° C. of each metal foil constituting the electromagnetic wave shielding material is 1.0 × 10 ⁶ S / m or more. .

  In still another embodiment of the electromagnetic wave shielding casing according to the first aspect of the present invention, the thickness of each metal foil constituting the electromagnetic wave shielding material is 4 to 50 μm.

  In still another embodiment of the electromagnetic wave shielding casing according to the first aspect of the present invention, the relative dielectric constant at 20 ° C. of each resin film constituting the electromagnetic wave shielding material is 2.0 to 10.0.

  In still another embodiment of the electromagnetic wave shielding casing according to the first aspect of the present invention, the thickness of each resin film constituting the electromagnetic wave shielding material is 4 to 500 μm.

  In still another embodiment of the electromagnetic wave shielding casing according to the first aspect of the present invention, the thickness of the thinnest portion of the resin casing main body is 0.5 mm or more.

In a second aspect, the present invention is a method of manufacturing an electromagnetic shielding casing comprising a resin casing main body and an electromagnetic shielding material for bonding and covering the inner surface and / or outer surface of the resin casing main body,
It has a multilayer structure in which at least one metal foil and at least one resin film are laminated, and at least one outermost layer is a resin film, and a film-like electromagnetic shielding material is set in a preform mold, A step of obtaining an electromagnetic wave shielding material preformed into a three-dimensional shape by pressure forming or vacuum forming;
In a state where the preformed electromagnetic wave shielding material is fitted into an injection mold having a cavity surface matching the three-dimensional shape of the electromagnetic wave shielding material so that the resin film forming the outermost layer is exposed in the cavity. Injecting the molten resin for the housing into the cavity of the injection mold, and solidifying by cooling, thereby integrating the preformed electromagnetic shielding material and the housing;
It is a manufacturing method containing.

  In one embodiment of the method for manufacturing an electromagnetic wave shielding casing according to the second aspect of the present invention, the outermost layer is formed, and the resin film exposed in the cavity is made of the same type of resin material as the resin casing body.

  In another embodiment of the method for producing an electromagnetic wave shielding casing according to the second aspect of the present invention, the electromagnetic shielding casing is the electromagnetic shielding casing according to the first aspect of the present invention.

  In another embodiment of the method for producing an electromagnetic wave shielding casing according to the second aspect of the present invention, in the step of obtaining the electromagnetic wave shielding material preformed in a three-dimensional shape, all the resins constituting the electromagnetic wave shielding material The film is subjected to pressure forming, vacuum forming or press forming in a state where the film is heated to a temperature lower than 20 ° C. below the heat deformation temperature of the resin film.

  In yet another embodiment of the method for manufacturing an electromagnetic wave shielding casing according to the second aspect of the present invention, in the step of integrating the preformed electromagnetic shielding material and the casing, the melting point of the injected resin is determined. A molten resin having a temperature higher than 5 ° C. and lower than a temperature exceeding the melting point of the injected resin by 100 ° C. is injected.

  In still another embodiment of the method for manufacturing an electromagnetic wave shielding casing according to the second aspect of the present invention, the thickness reduction rate of the electromagnetic shielding material is set to 16% or more in the pressure forming or vacuum forming.

In a third aspect, the present invention is a method for manufacturing an electromagnetic shielding casing comprising a resin casing main body, and an electromagnetic shielding material that covers and covers the inner surface and / or outer surface of the resin casing main body,
A film-like electromagnetic shielding material having a multilayer structure in which at least one metal foil and at least one resin film are laminated, and at least one outermost layer being a resin film, defines a three-dimensional shape of the electromagnetic shielding material A molten resin injection port in which a resin film for forming an outermost layer is installed in a second mold in an injection mold having a first mold having projections and depressions and a second mold having an injection port And the process of setting to face each other,
A step of obtaining a preformed electromagnetic wave shielding material by moving both molds to the position at the time of injection molding;
By injecting molten resin for the housing from the injection port provided in the second mold, the electromagnetic shielding material is made to follow the unevenness of the first mold by injection pressure, and then cooled and solidified. Integrating the molded electromagnetic shielding material and the housing;
It is a manufacturing method containing.

  The manufacturing method of the electromagnetic wave shielding housing | casing which concerns on the 3rd side surface of this invention WHEREIN: In one Embodiment, the outermost layer is formed and the resin film which faces an injection port consists of the same kind of resin material as a resin-made housing body.

  In another embodiment of the method for producing an electromagnetic wave shielding casing according to the third aspect of the present invention, the electromagnetic shielding casing is the electromagnetic shielding casing according to the first aspect of the present invention.

  In still another embodiment of the method for manufacturing an electromagnetic wave shielding casing according to the third aspect of the present invention, the total thickness reduction rate of the electromagnetic wave shielding material in the preforming and the main molding is set to 16% or more.

  The electromagnetic wave shielding material used in the electromagnetic wave shielding casing according to the present invention has a configuration in which a resin film is adhered and laminated on a metal foil. In addition to using a thin material such as a metal foil, the electromagnetic shielding material is easily stretched because the metal foil is in close contact with the resin film. For this reason, the electromagnetic wave shielding housing according to the present invention can be manufactured by insert molding or in-mold molding using pressure forming or vacuum forming. And since it becomes easy to extend | stretch metal foil, since the fracture | rupture of metal foil is suppressed at the time of shaping | molding, the electromagnetic wave leakage which may arise in a fracture location is also suppressed. Further, by laminating a plurality of metal foils via a resin film, it is possible to achieve both lightness and excellent electromagnetic shielding properties.

  Moreover, in the electromagnetic wave shielding housing according to the present invention, since the bonding interface between the electromagnetic wave shielding material and the resin housing body is made of resin, a high bonding strength between the electromagnetic wave shielding material and the resin housing body is ensured. It becomes possible to do.

The example of the manufacture procedure of the electromagnetic wave shielding housing | casing which concerns on this invention using film insert molding is shown typically. The example of the manufacture procedure of the electromagnetic wave shielding housing | casing which concerns on this invention using in-mold shaping | molding is shown typically. The result of the magnetic field shield effect evaluation test in Test Example 2 is shown. The laminated structure of the electromagnetic shielding material (a)-(d) used for the magnetic field shield effect evaluation test in Test Example 3 is shown. The laminated structure of the electromagnetic shielding material (e)-(i) used for the magnetic field shield effect evaluation test in Test Example 3 is shown. The laminated structure of electromagnetic wave shielding material (j)-(m) used for the magnetic field shield effect evaluation test in Test Example 3 is shown. The result of the magnetic field shielding effect evaluation test in Test Example 3 is shown ((a) to (d)). The result of the magnetic field shield effect evaluation test in Test Example 3 is shown ((e) to (i)). The result of the magnetic field shield effect evaluation test in Test Example 3 is shown (comparison of (a), (b), (e), and (f)). The result of the magnetic field shielding effect evaluation test in Test Example 3 is shown ((j) to (m)).

(Metal foil)
Although there is no restriction | limiting in particular as a material of metal foil used for the shielding material of the electromagnetic wave shielding housing | casing which concerns on this invention, From a viewpoint of improving the shielding characteristic with respect to an alternating current magnetic field or an alternating current electric field, it shall be a metal material excellent in electroconductivity. Is preferred. Specifically, it is preferably formed of a metal having an electrical conductivity of 1.0 × 10 ⁶ S / m (a value at 20 ° C., the same shall apply hereinafter), and the electrical conductivity of the metal is 10.0 × 10 ⁶ S / m. m is more preferably 30.0 × 10 ⁶ S / m or more, and most preferably 50.0 × 10 ⁶ S / m or more. Such metals include iron conductivity of about 9.9 × 10 ⁶ S / m, the conductivity of about 14.5 × 10 ⁶ S / m of nickel, the conductivity of about 39.6 × 10 ⁶ S Aluminum having a conductivity of about 58.0 × 10 ⁶ S / m, and silver having a conductivity of about 61.4 × 10 ⁶ S / m. Considering both conductivity and cost, it is preferable in practical use to use aluminum or copper. The metal foil used for the shield material according to the present invention may all be the same metal, or a different metal may be used for each layer. Moreover, the metal alloy mentioned above can also be used. Various surface treatment layers for the purpose of adhesion promotion, environmental resistance, heat resistance and rust prevention may be formed on the surface of the metal foil.

  For example, Au plating, Ag plating, Sn plating, Ni plating, Zn plating, Sn alloy plating (Sn-Ag) for the purpose of enhancing the environmental resistance and heat resistance required when the metal surface is the outermost layer. , Sn-Ni, Sn-Cu, etc.), chromate treatment, and the like. These processes may be combined. From the viewpoint of cost, Sn plating or Sn alloy plating is preferable.

  Further, for the purpose of enhancing the adhesion between the metal foil and the resin film, chromate treatment, roughening treatment, Ni plating and the like can be performed. These processes may be combined. Roughening treatment is preferable because adhesion can be easily obtained.

  In addition, a metal layer having a high relative permeability can be provided for the purpose of enhancing the shielding effect against a DC magnetic field. Examples of the metal layer having a high relative magnetic permeability include Fe—Ni alloy plating and Ni plating.

  When using copper foil, since a shield performance improves, a thing with high purity is preferable, and purity is preferably 99.5 mass% or more, More preferably, it is 99.8 mass% or more. As the copper foil, a rolled copper foil, an electrolytic copper foil, a copper foil by metallization, or the like can be used, and a rolled copper foil excellent in flexibility and moldability is preferable. When alloy elements are added to the copper foil to obtain a copper alloy foil, the total content of these elements and inevitable impurities may be less than 0.5% by mass. In particular, when the copper foil contains at least one selected from the group consisting of Sn, Mn, Cr, Zn, Zr, Mg, Ni, Si, and Ag in a total amount of 200 to 2000 ppm by mass, pure copper foil having the same thickness This is preferable because the elongation is further improved.

  The thickness of the metal foil used for the shield material according to the present invention is preferably 4 μm or more per sheet. If it is less than 4 μm, the ductility of the metal foil is remarkably lowered, and the molding processability of the shield material may be insufficient. Further, if the thickness of the foil per sheet is less than 4 μm, it is necessary to laminate a large number of metal foils in order to obtain an excellent electromagnetic wave shielding effect, which causes a problem that the manufacturing cost increases. From such a viewpoint, the thickness of the metal foil is more preferably 10 μm or more, still more preferably 15 μm or more, still more preferably 20 μm or more, and further preferably 25 μm or more. More preferably, it is 30 μm or more. On the other hand, the thickness of the metal foil is preferably 100 μm or less, more preferably 50 μm or less, because the moldability deteriorates even if the thickness of the metal foil per sheet exceeds 100 μm. Is more preferably 45 μm or less, and still more preferably 40 μm or less.

  From the viewpoint of improving the shielding performance, it is preferable to laminate a plurality of metal foils constituting the shielding material via a resin film. However, if there are two metal foil layers, the total thickness of the metal foil required to obtain a magnetic field shielding characteristic of 25 dB or more in a low frequency region with a frequency of about 1 MHz will increase. Since the thickness of the foil is increased, the moldability is adversely affected. For this reason, it is more preferable to laminate three or more metal foils from the viewpoint of ensuring excellent electromagnetic wave shielding characteristics while reducing the total thickness of the metal foil. By laminating three or more metal foils, even when the total thickness of the metal foils is the same, the shielding effect is remarkably improved as compared with the case where the metal foil is a single layer or when two metal foils are laminated. On the other hand, the higher the number of laminated metal foils, the better the electromagnetic shielding properties. However, increasing the number of laminated layers increases the number of lamination processes, leading to increased manufacturing costs, and the effect of improving shielding tends to be saturated. The number of metal foils constituting the material is preferably 5 or less, more preferably 4 or less.

  Therefore, in one embodiment of the shielding material according to the present invention, the total thickness of the metal foil can be 15 to 150 μm, can be 100 μm or less, can be 80 μm or less, and can be 60 μm or less. You can also.

(Resin film)
By closely laminating a plurality of metal foils via a resin film, the electromagnetic wave shielding effect can be remarkably improved, and the moldability is significantly improved because the metal foil is prevented from being broken. It is possible to manufacture a three-dimensional shielding material having both light weight and excellent electromagnetic shielding properties by using compressed air molding or vacuum molding. Even if the metal foils are directly stacked, the shielding effect is improved by increasing the total thickness of the metal foils, but a remarkable improvement effect cannot be obtained. This is presumably because the presence of the resin film between the metal foils increases the number of reflections of the electromagnetic wave and attenuates the electromagnetic wave. Further, even if the metal foils are directly stacked, it is not possible to obtain the effect of improving the moldability.

  A resin film having a larger impedance difference from the metal foil is preferable for obtaining an excellent electromagnetic shielding effect. In order to produce a large impedance difference, it is necessary that the relative dielectric constant of the resin film is small, and specifically, it is preferably 10 (20 ° C. value; the same shall apply hereinafter) or less, preferably 5.0 or less. Is more preferable, and it is still more preferable that it is 3.5 or less. In principle, the dielectric constant is never less than 1.0. Generally, it is about 2.0 at least for materials that can be obtained, and even if it is further lowered and approaches 1.0, the increase in shielding effect is limited, but the material itself becomes special and expensive. It becomes. Considering the balance between cost and effect, the relative dielectric constant is preferably 2.0 or more, and more preferably 2.2 or more.

  The material constituting the resin film is preferably a synthetic resin from the viewpoint of processability. The resin film can be mixed with fiber reinforcing materials such as carbon fiber, glass fiber, and aramid fiber. Synthetic resins include polyesters such as PET (polyethylene terephthalate), PEN (polyethylene naphthalate) and PBT (polybutylene terephthalate), olefinic resins such as polyethylene and polypropylene, polyamides, from the viewpoint of availability and processability. Polyimide, liquid crystal polymer, polyacetal, fluorine resin, polyurethane, acrylic resin, epoxy resin, silicone resin, phenol resin, melamine resin, ABS resin, polyvinyl alcohol, urea resin, polyvinyl chloride, polycarbonate, polystyrene, styrene butadiene rubber, etc. Of these, PET, PEN, polyamide, and polyimide are preferred for reasons of processability and cost. The synthetic resin may be an elastomer such as urethane rubber, chloroprene rubber, silicone rubber, fluoro rubber, styrene, olefin, vinyl chloride, urethane, and amide. Of these, polyamide, polycarbonate, polystyrene, etc., which are often used for injection molding and can be easily integrated, can be suitably used.

  The thickness of the resin film is not particularly limited, but if the thickness per sheet is less than 4 μm, the (elongation) breaking strain of the shielding material tends to decrease, so the thickness per resin film is 4 μm or more. It is preferably 7 μm or more, more preferably 10 μm or more, even more preferably 20 μm or more, still more preferably 40 μm or more, and further preferably 80 μm or more. And more preferably 100 μm or more. On the other hand, even if the thickness per sheet exceeds 600 μm, the (elongation) breaking strain of the shielding material tends to decrease. Therefore, the thickness of one resin film is preferably 600 μm or less, and more preferably 500 μm or less.

  Examples of the method of closely laminating the resin film and the metal foil include thermocompression bonding, ultrasonic bonding, bonding with an adhesive, and a method of forming a film by applying and curing a molten resin on the metal foil. Among these, thermocompression bonding is preferable because of the stability of the adhesive strength in the molding processing temperature region. Thermocompression bonding is a method in which a metal foil and a resin film are brought into close contact with each other by applying pressure after heating to a melting point of the resin film or lower, thereby causing plastic deformation and joining. It is also preferable to employ thermonic bonding in which thermocompression bonding is performed while applying ultrasonic vibration. It is also possible to laminate closely through an adhesive, but when using an adhesive, there is a possibility of softening by the heat when injection molding the casing and reducing the adhesion strength between the metal foil and the resin film . For this reason, thermocompression bonding is preferred. At the time of thermocompression bonding, from the viewpoint of enhancing the adhesion between the resin film and the metal foil, it is preferable that all the resin films constituting the electromagnetic wave shielding material are heated to a temperature lower than the melting point of the resin film by 30 ° C. or more. It is more preferable to heat to a temperature below 10 ° C., and it is even more preferable to heat to a temperature below the melting point by 10 ° C. However, if heated more than necessary, the resin film melts and is extruded under pressure, resulting in loss of thickness uniformity and physical properties. Therefore, heating during thermocompression is performed on all resin films constituting the electromagnetic shielding material. The temperature is preferably 20 ° C. or less higher than the melting point of the film, more preferably 10 ° C. or less higher than the melting point of the resin film, and even more preferably less than the melting point of the resin film. In addition, the pressure during thermocompression bonding is preferably 0.05 MPa or more, more preferably 0.1 MPa or more, and more preferably 0.15 MPa or more from the viewpoint of improving the adhesion between the resin film and the metal foil. Even more preferred. However, even if the pressure is increased more than necessary, not only the adhesion is not improved, but also the resin film is deformed and the thickness uniformity is impaired. Therefore, the pressure during thermocompression bonding is preferably 60 MPa or less, and 45 MPa. More preferably, it is more preferably 30 MPa or less.

(Electromagnetic wave shielding material)
The electromagnetic shielding material (also simply referred to as “shielding material”) is preferably formed of a molded body having a structure in which two or more, more preferably three or more metal foils are laminated via a resin film. Moreover, in order for a shield material to join with the inner surface and / or outer surface of a resin housing main body, the layer which forms a joint surface with a housing | casing needs to be comprised with a resin film. The following is mentioned as an example of the laminated structure of the electromagnetic wave shielding material which comprises these requirements.
(1) Metal foil / resin film / metal foil / resin film to be bonded to casing (2) Resin film / metal foil / resin film / metal foil / resin film to be bonded to casing (3) Metal foil / resin film / Metal foil / resin film / metal foil / resin film to be bonded to casing (4) resin film / metal foil / resin film / metal foil / resin film / metal foil / resin film to be bonded to casing

  In (1) to (4), one “metal foil” can be formed by laminating a plurality of metal foils without using a resin film, and one “resin film” can also be formed without using a metal foil. A plurality of resin films can be laminated. That is, a plurality of metal foils laminated without a resin film can be regarded as a single metal foil, and a plurality of resin films laminated without a metal foil can be regarded as a single resin film. it can. Moreover, layers other than a resin film and metal foil can also be provided.

  However, from the viewpoint of moldability, each metal foil constituting the electromagnetic shielding material is preferably sandwiched on both sides by a resin film. Since both surfaces of each metal foil are sandwiched between resin films, the effect of preventing breakage during molding can be enhanced. That is, both the outermost layers of the laminated body than the aspect in which the metal foil forms the outermost layer of the electromagnetic wave shielding material or the aspect in which the plurality of metal foils are laminated without interposing the resin film in the inner layer of the electromagnetic wave shielding material Is preferably a resin film, and the resin film and the metal foil are alternately laminated one by one.

  In one embodiment, the electromagnetic shielding material according to the present invention can be formed without breakage even in a process with a thickness reduction rate of 16% or more, and preferably molded without breakage even in a process with a thickness reduction rate of 20% or more. More preferably, it can be formed without breaking even when the thickness reduction rate is 25% or more. For example, the thickness reduction rate is 16 to 40%, typically 20 to 30%. In the present invention, the ruptured state of both the metal foil and the resin film is evaluated by observing the electromagnetic wave shielding material after molding with an X-ray CT observation apparatus.

It is also possible to select the metal foil and the resin film so that all combinations of the metal foil and the resin film constituting the electromagnetic wave shielding material satisfy σ _M × d _M × d _R ≧ 3 × 10 ^−3. It is preferable from the viewpoint of remarkably enhancing the shielding effect.

Various symbols used in this specification are defined as follows including the above-mentioned σ _M , d _M , and d _R.
σ _M : conductivity of metal foil at 20 ° C. (S / m)
d _M : Metal foil thickness (m)
Z _R : impedance of resin film (Ω) = Z ₀ × √ (1 / ε _R )
ε _R : relative dielectric constant γ _R of resin film at 20 ° C .: propagation constant = j × 2π√ (ε _R / λ); j is imaginary unit λ: wavelength (m): 300 m at 1 MHz
d _R : thickness of resin film (m)
Z ₀ : Impedance of vacuum = 377Ω

The shield characteristic can be expressed by the following relationship using a four-terminal matrix, where the electric field of the incident wave is E _x ⁱ , the magnetic field is H _x ⁱ , the electric field of the transmitted wave is E _x ^t , and the magnetic field is H _x ^t. it can.

In this case, the shield effect (SE) can be expressed by the following equation using the Schelkunoff equation.

When metal foil is used as a constituent element of the shield material, a = 1, b = 0, c = σ _M × d _M , and d = 1. Substituting this into equation 1, the following equation is obtained.

When using a resin film as a component of the shielding material may be _{a = 1, b = Z R} × γ R × d R, c = γ R × d R / Z R, and d = 1 to. Substituting this into equation 1, the following equation is obtained.

Furthermore, the shielding characteristic when the resin film and the metal foil are laminated is theoretically obtained by the product of the four-terminal matrix corresponding to each layer. For example, an incident wave and a transmitted wave when a shield material is configured by a laminated structure of metal (M1) / resin (R1) / metal (M2) can be expressed by the following equations.

In addition, the incident wave and the transmitted wave when the shield material is configured by a laminated structure of metal (M1) / resin (R1) / metal (M2) / resin (R2) / metal (M3) can be expressed by the following equations. it can.

When this is expanded, the following equation is obtained.
Here, A, B, C and D are as follows.
_{A = 1 + Z R1 γ R1} d R1 σ M2 d M2 + Z R2 γ R2 d R2 σ M3 d M3 + Z R1 γ R1 d R1 σ M3 d M3 + Z R1 γ R1 d R1 Z R2 γ R2 d R2 σ M2 d M2 σ M3 d _{M3
B = Z R2 γ R2 d R2} + Z R1 γ R1 d R1 Z R2 γ R2 d R2 σ M2 d M2 + Z R1 γ R1 d R1
_{C = σ M1 d M1 + σ} M2 d M2 + σ M3 d M3 + γ R1 d R1 / Z R1 + γ R2 d R2 / Z R2 + Z R1 γ R1 d R1 σ M1 d M1 + Z R1 γ R1 d R1 σ M1 d M1 σ M3 _{d M3 + Z R1 γ R1 d} R1 Z R2 γ R2 d R2 σ M1 d M1 σ M2 d M2 σ M3 d M3 + Z R2 γ R2 d R2 σ M2 d M2 σ M3 d M3 + Z R2 γ R2 d R2 σ M3 d M3 γ _R1 d _R1 / Z _{R1
D = Z R2 γ R2 d R2} σ M1 d M1 + Z R2 γ R2 d R2 σ M1 d M1 σ M2 d M2 + Z R2 γ R2 d R2 σ M2 d M2 + Z R1 γ R1 d R1 σ M1 d M1 + Z R2 γ R2 d _R2 γ _R1 d _R1 / Z _R1

From the above illustration, the shielding effect in the laminate of the metal foil and the resin film is obtained by increasing σ _M × d _M × Z _R × γ _R × d _R for all combinations of the metal foil and the resin film to be used. It can be theoretically understood that it can be improved. However, as described in, for example, “Kenichi Hatakeyama,“ Electromagnetic shielding course for the first time ”Science Information Publishing (2013), p. 56”, conventionally (Z _R × γ _R × d _R ) is in the low frequency range. Therefore, according to this concept, σ _M × d _M × Z _R × γ _R × d _R is also a parameter that can be approximated to 0. By adjusting d _R , σ _M, and d _M by combining an appropriate metal foil and resin film, σ _M × d _M × Z _R × γ _R × d _R becomes a large value that cannot be approximated to 0, and is low. It was found that there was a significant effect even in the frequency domain.

The present inventor repeated the experiment of the shielding effect in the laminate of the metal foil and the resin film, and that σ _M × d _M × d _R has a significant influence even in a low frequency region of about 1 MHz. It is possible to select the metal foil and the resin film so that all combinations of the metal foil and the resin film constituting the heading and the electromagnetic wave shielding material satisfy σ _M × d _M × d _R ≧ 3 × 10 ^−3. It was found to be extremely effective in increasing It is preferable that all combinations of the metal foil and the resin film constituting the electromagnetic shielding material satisfy σ _M × d _M × d _R ≧ 1 × 10 ⁻² , and σ _M × d _M × d _R ≧ 4 × 10 ^{−. 2} is more preferable, σ _M × d _M × d _R ≧ 8 × 10 ⁻² is still more preferable, and σ _M × d _M × d _R ≧ 1 × 10 ⁻¹ is even more preferable. preferable.

No particular upper limit is set for σ _M × d _M × d _R , but in general, all combinations of metal foil and resin film constituting the electromagnetic wave shielding material are considered to be σ _M × in consideration of the thickness and the material used. d _M × d _R ≦ 10, typically σ _M × d _M × d _R ≦ 1.

  In one embodiment of the electromagnetic wave shielding material according to the present invention, the total thickness of the electromagnetic wave shielding material can be 50 to 1500 μm, can be 1000 μm or less, can be 600 μm or less, and can be 400 μm or less. It can also be 300 micrometers or less, and can also be 250 micrometers or less.

  According to one embodiment of the electromagnetic wave shielding material according to the present invention, it can have a magnetic field shielding characteristic of 25 dB or more (how much the signal has been attenuated on the receiving side) at 1 MHz, and preferably has a magnetic field shielding characteristic of 30 dB or more. More preferably 40 dB or more, even more preferably 50 dB or more, even more preferably 60 dB or more. For example, it can have a magnetic field shielding characteristic of 36 to 90 dB. In the present invention, the magnetic field shield characteristic is measured by the KEC method. The KEC method refers to the “electromagnetic shielding characteristic measurement method” at the Kansai Electronics Industry Promotion Center.

(Electromagnetic wave shielding housing)
The electromagnetic wave shielding casing according to the present invention can be manufactured by film insert molding or in-mold molding. In the present invention, from the viewpoint of weight reduction, the material constituting the housing body is made of a resin material, and it is necessary to join an electromagnetic shielding material to the housing body. The resin used for the housing body needs to have a considerable thickness from the viewpoint of securing strength, and is difficult to perform pressure forming or vacuum forming.

  The resin constituting the housing body is the same type of resin as the resin film that forms the joint surface of the electromagnetic shielding material with the housing body from the viewpoint of securing the bonding strength at the interface between the housing body and the electromagnetic shielding material, that is, It is desirable to use a resin having a common chemical structure at the portion where the monomers are bonded. For example, if the resin film of the electromagnetic shielding material that forms the joint surface with the housing body is made of polyester that bonds the monomers to each other by ester bonds, the housing body is also preferably made of polyester, and the joint surface with the housing body is If the resin film of the electromagnetic shielding material to be formed is made of polyimide that bonds monomers by imide bonds, the housing body is also preferably made of polyimide, and the electromagnetic shielding material that forms the joint surface with the housing main body If the resin film is made of polyamide in which monomers are bonded to each other by an amide bond, the housing body is preferably made of polyamide. However, the difference in fiber reinforcing materials such as carbon fiber, glass fiber, and aramid fiber and the difference in other additives are not limited.

  Furthermore, it is more preferable that the material constituting the housing body has a monomer unit in common with the resin film that forms a joint surface with the housing of the electromagnetic shielding material. For example, if the resin film of the electromagnetic wave shielding material that forms the joint surface with the casing body is made of PET, the casing body is also preferably made of PET.

  Further, from the viewpoint of bonding strength, the melting point of the resin film of the electromagnetic wave shielding material that forms the bonding surface with the housing body is preferably within ± 20 ° C. with respect to the melting point of the resin constituting the housing body. More preferably, it is within ± 10 ° C, and even more preferably within ± 5 ° C. The melting point of the resin film of the electromagnetic wave shielding material that forms the joint surface with the housing body is close to the melting point of the resin constituting the housing body, so that an advantage that it is easy to integrate at the time of injection molding can be obtained.

  The melting point of the resin is defined as a temperature showing an endothermic peak due to melting when a DSC curve is created by a differential scanning calorimeter. When the resin shows a plurality of endothermic peaks such as a polymer alloy, it is defined as the lowest temperature among the temperatures showing the heat peaks.

  The thickness of the resin constituting the housing body is preferably 0.5 mm or more, more preferably 0.8 mm or more, even at the thinnest part, from the viewpoint of securing the strength as the housing. Even more preferably. Although there is no restriction | limiting in particular in the upper limit of the thickness of resin which comprises a housing body, From a viewpoint of weight reduction and size reduction, it is preferable that it is 200 mm or less, it is more preferable that it is 150 mm or less, and it is 100 mm or less. Even more preferred.

An example of a specific manufacturing procedure of the electromagnetic wave shielding casing according to the present invention using film insert molding will be described below with reference to FIG.
(1. Molding of preform)
First, a film shape having a multilayer structure in which at least one metal foil and at least one resin film are laminated, and at least one outermost layer being a resin film made of the same type of resin material as the resin casing body The electromagnetic wave shielding material 11 is preformed into a three-dimensional shape by setting the electromagnetic wave shielding material 11 in a preform mold 12 (step (a)), and performing pressure forming or vacuum forming (step (b)). To obtain (step (c)).

  Pressure forming or vacuum forming facilitates deformation of the electromagnetic shielding material and reduces the thermal deformation temperature of the resin film by 20 ° C. for all the resin films constituting the electromagnetic shielding material in order to improve the followability to the mold. It is preferably carried out in a state heated to a temperature equal to or higher than the temperature, more preferably carried out in a state heated to a temperature lower than the thermal deformation temperature of the resin film by 10 ° C. or more, a state heated above the thermal deformation temperature of the resin film. Even more preferably, On the other hand, if the temperature is too high, the strength of the resin film will be too low to hold the metal foil, and the metal foil will be easily broken, so the melting point of the resin film for all the resin films constituting the electromagnetic wave shielding material It is preferable to carry out in a state heated to a temperature below 10 ° C, more preferably to a temperature below a melting point of the resin film of 15 ° C or less, and heat to a temperature below the melting point of the resin film by 20 ° C or less. It is even more preferable to carry out in such a state.

Here, the thermal deformation temperature (the deflection temperature under load) of the resin is a temperature defined by JIS K7191-2007. When a sample of 80 mm × 20 mm and a thickness of 4 mm was placed on a sample table with a fulcrum distance of 64 mm by a heat distortion tester, a bending load of 18.6 kg / cm ² was applied and the temperature was raised at 2 ° C./min, the resin film It is defined as the temperature when the deflection is 0.34 mm.

(2. Injection molding)
Next, the preformed electromagnetic shielding material 13 is introduced into an injection mold 14 having a cavity surface that matches the three-dimensional shape of the electromagnetic shielding material 13 (step (d)), and is the same as the resin casing body. With the resin film made of various types of resin material fitted in the cavity so as to be exposed, the molten resin for the housing is injected into the cavity of the mold for injection molding, and is cooled and solidified. The electromagnetic shielding material and the housing are integrated (step (e)), and the integrally molded product is taken out from the mold (step (f)).

  When injecting a molten resin, in order to improve the fluidity of the molten resin, it is preferable that the temperature of the injected resin be equal to or higher than the melting point of the resin, and more preferable that the temperature be higher than the melting point by 5 ° C. It is even more preferable to set the melting point to 10 ° C. or higher. Further, when injecting the molten resin, in order to prevent the resin from being deteriorated by heat and to stabilize the quality, it is preferable that the temperature of the injected resin is not more than 300 ° C. and the melting point is 250 ° C. More preferably, the temperature is less than or equal to ℃, and even more preferably, the melting point is less than or equal to 200 ℃.

  When injecting the molten resin, in order to prevent internal defects such as voids, the injection pressure is preferably 20 MPa or more, more preferably 25 MPa or more, and even more preferably 30 MPa or more. If the pressure is too high, burrs are likely to be generated. Therefore, the injection pressure is preferably 400 MPa or less, more preferably 350 MPa or less, and even more preferably 300 MPa or less. The injection pressure refers to the pressure applied to the resin injected into the mold.

Next, an example of a specific manufacturing procedure of the electromagnetic wave shielding casing according to the present invention using in-mold molding will be described below with reference to FIGS.
(1. Pre-molding)
First, a film shape having a multilayer structure in which at least one metal foil and at least one resin film are laminated, and at least one outermost layer being a resin film made of the same type of resin material as the resin casing body The electromagnetic shielding material 21 is set between the first mold 22a and the second mold 22b of the injection mold 22 (step (a ')). At this time, the electromagnetic shielding material 21 is set so that the resin film made of the same type of resin material as the resin casing body faces the molten resin injection port 23 installed in the second mold 22b. Next, both molds are moved to the position at the time of injection molding (step (b ′)). The first mold 22a has irregularities for defining the three-dimensional shape of the electromagnetic shielding material 21, and the electromagnetic shielding material 21 does not follow the fine irregularities of the first mold 22a by step (b ′). However, it is preformed roughly along the first mold 22a of an injection molded product.

(2. Main molding)
Next, the molten resin for the casing is injected from the injection port 23 provided in the second mold 22b, and the electromagnetic shielding material 21 is made to follow the fine unevenness of the first mold 22a by the injection pressure, thereby performing the main molding. To do. The molten resin is cooled and solidified in the mold 22 to integrate the molded electromagnetic shielding material and the casing (step (c ′)). Thereafter, the integrally molded product 25 is taken out from the injection mold 22 (step (d ′)).

  When injecting a molten resin, in order to improve the fluidity of the molten resin, it is preferable that the temperature of the injected resin be equal to or higher than the melting point of the resin, and more preferable that the temperature be higher than the melting point by 5 ° C. It is even more preferable to set the melting point to 10 ° C. or higher. Further, when injecting the molten resin, in order to prevent the resin from being deteriorated by heat and to stabilize the quality, it is preferable that the temperature of the injected resin is not more than 300 ° C. and the melting point is 250 ° C. More preferably, the temperature is less than or equal to ℃, and even more preferably, the melting point is less than or equal to 200 ℃.

  When injecting the molten resin, in order to prevent internal defects such as voids, the injection pressure is preferably 20 MPa or more, more preferably 25 MPa or more, and even more preferably 30 MPa or more. If the pressure is too high, burrs are likely to be generated. Therefore, the injection pressure is preferably 400 MPa or less, more preferably 350 MPa or less, and even more preferably 300 MPa or less. The injection pressure refers to the pressure applied to the resin injected into the mold.

  The integrally molded product obtained by film insert molding or in-mold molding can constitute a part of the electromagnetic shielding casing, for example, the lower half. If necessary, the electromagnetic wave shielding casing can be manufactured by forming the remaining part, for example, an integrally molded product constituting the upper half part by the same procedure, and connecting them together.

  The electromagnetic shielding casing according to the present invention is particularly an electric / electronic device (for example, an inverter, a communication device, a resonator, an electron tube / discharge lamp, an electric heating device, an electric motor, a generator, an electronic component, a printed circuit, a medical device, etc.). Can be accommodated, and can be applied to applications that block electromagnetic waves emitted from electrical and electronic equipment.

  Examples of the present invention are shown below together with comparative examples, which are provided for a better understanding of the present invention and its advantages, and are not intended to limit the invention.

<Test Example 1: Applicability evaluation of film insert molding>
(Examples 1-1 to 1-4>
The following materials were prepared as a metal foil and a resin film.
Cu: rolled copper foil (conductivity at 20 ° C .: 58.0 × 10 ⁶ S / m, thickness: see Table 1)
Al: Aluminum foil (conductivity at 20 ° C .: 39.6 × 10 ⁶ S / m, thickness: see Table 1)
PA: Polyamide film (nylon 6, relative dielectric constant at 20 ° C .: 3.7, heat distortion temperature: 75 ° C., melting point: 300 ° C., thickness: see Table 1)
After laminating these metal foils and resin films in the order of lamination shown in Table 1, thermocompression bonding was performed at a pressure of 6 MPa at 295 ° C. for 30 minutes without using an adhesive, and the metal foils and resin films were adhered and laminated. An electromagnetic shielding material was obtained.
<Comparative Examples 1-1 to 1-3>
Moreover, the following electromagnetic wave shielding materials were prepared for comparison.
Copper plate: conductivity at 20 ° C .: 58.0 × 10 ⁶ S / m, thickness: see Table 1 Aluminum plate: conductivity at 20 ° C .: 39.6 × 10 ⁶ S / m, thickness: see Table 1 The electrical conductivity was measured by the double bridge method of JIS C2525: 1999. The relative dielectric constant was measured by the B method described in JIS C 2151: 2006. The melting point of the resin film was measured with a differential scanning calorimeter (DSC-3100SA manufactured by NETZSCH) according to the above-mentioned criteria. The heat distortion temperature of the resin film was measured by the heat distortion tester (Toyo Seiki Seisakusho 3M-2) according to the above-mentioned standard.

(Magnetic shield effect)
The above electromagnetic shielding material was installed in a magnetic field shielding effect evaluation apparatus (Techno Science Japan, Inc., model TSES-KEC), and the magnetic field shielding effect at 200 kHz was evaluated by the KEC method under the condition of 25 ° C. The results are shown in Table 1. The case where the magnetic field shielding effect was 25 dB or more was rated as ◎, the case where it was 23 dB or more and less than 25 dB was marked as ◯, and the case where it was less than 23 dB was marked as x.

(Molding test)
For each electromagnetic shielding material cut into 90mm x 90mm under the conditions of a mold temperature of 150 ° C and a pressure of 1MPa in a mold that makes a hemisphere with a radius of 30mm by using a pressure forming tester (made by Kitaguchi Seiki Co., Ltd., special order) A molding test was conducted. In Examples 1-1 to 1-4, molded articles were prepared so that the outer peripheral surface side of the hemisphere was a polyamide film having a thickness of 50 μm (the rightmost PA in Table 1). The case where the electromagnetic shielding material was broken during the molding test was rated as x, and the case where it was not broken was marked as ◯. The thickness of the resin film and metal foil after the molding test was measured by cross-sectional observation. The presence or absence of cracks is not only the resin film on both sides constituting the outermost layer, but also X-ray CT (micro CT scanner manufactured by Toshiba IT Control System, TOSCANER 32251 μhd, tube current 120 μA, tube voltage 80 kV) and the resin film and metal inside the electromagnetic shielding material This was confirmed by observing the foil. Moreover, the case where the depth of the molded article obtained by the said test was 40 mm or more was set as (circle), and the case where it was less than 40 mm was set as x. If it has excellent flexibility and ductility, a molded product having a depth of 40 mm or more can be molded with the above pressure. The results are shown in Table 1.

(Joining test)
A test for evaluating the bonding strength between the electromagnetic shielding material and the resin casing body was performed according to the following procedure. Polyamide resin (nylon 6, relative dielectric constant at 20 ° C .: 3.7, melting point: 300 ° C. heat distortion temperature: 75 ° C.) on the outer peripheral surface of the hemispherical molded product obtained in the above molding test Was injection molded (injection temperature: 320 ° C., injection pressure: 120 MPa) to obtain a hemispherical molded product and an integrally molded product of polyamide resin. The joint strength between the hemispherical molded product and the polyamide resin was measured by performing a 180 degree peel test specified in JIS Z0237-2009 on the obtained integrally molded product. The case where the bonding strength was 20 N / 25 mm or more was evaluated as ◯, the case where it was 1 N / 25 mm or more and less than 20 N / 25 mm, and the case where it was less than 1 N / 25 mm, or x. However, for Example 1-4, ABS resin (relative dielectric constant at 20 ° C .: 3.0, melting point: 110 ° C.) was injection molded (injection temperature 250 ° C., injection pressure 100 MPa), and hemispherical molded product An integrally molded product of ABS resin was obtained. The results are shown in Table 1.

<Test Example 2: Investigation of magnetic shielding effect in a single layer>
The magnetic shielding effect of a single layer was investigated for various metals. The metal materials used are as follows.
(1) Rolled copper foil (thickness: 280 μm)
(2) Rolled copper foil (thickness: 150 μm)
(3) Zn-plated steel plate (thickness: 270 μm)
(4) Silicon steel plate (thickness: 330 μm)
(5) SUS304 (thickness: 330 μm)
(6) SUS430 (thickness: 150 μm)
(7) Aluminum (thickness: 300 μm)
The prepared metal material was installed in a magnetic field shielding effect evaluation apparatus (Techno Science Japan Co., Ltd. Model TSES-KEC), and the magnetic field shielding effect was evaluated by the KEC method under room temperature (25 ° C.) conditions. At this time, the frequency was changed from 0.1 MHz to 1000 MHz, and the transition of the magnetic field shielding effect with respect to the change in frequency was investigated.

  The results are shown in FIG. It can be seen that copper having higher conductivity than the iron-based material gives a higher shielding effect if the thickness is the same. Moreover, if the same material is used, it can be seen that the greater the thickness, the higher the shielding effect. Among these materials, only the rolled copper foil having a thickness of 280 μm and the aluminum having a thickness of 300 μm were able to achieve a magnetic field shielding characteristic of 36 dB or more in the entire region of 1 MHz to 1000 MHz. As can be seen from these results, it is necessary to considerably increase the thickness in order to obtain an excellent magnetic field shielding effect with the metal material alone. Such a thick metal foil is inferior in moldability and heavy, and thus cannot be said to be highly practical.

<Test Example 3: Relationship between the number of laminated metal foils and the magnetic shielding effect>
A 12 μm thick polyethylene terephthalate (PET) film (relative dielectric constant: 3.2 at 25 ° C.) was used as the resin film, and a rolled copper foil (conductivity at 20 ° C .: 58.25 μm) as the metal foil. 0 × 10 ⁶ Ω · m) and 30 μm or 60 μm thick aluminum foil (conductivity at 20 ° C .: 39.6 × 10 ⁶ Ω · m), and FIGS. Each of the electromagnetic shielding materials having the laminated structure shown in FIG. The conductivity was measured by the double bridge method of JIS C2525: 1999 for both copper foil and aluminum foil. About the interface which laminated | stacked metal foil and PET film through the adhesive agent, it has displayed as "adhesive agent" in FIGS. As the adhesive, a urethane adhesive of Adlock RU-80 / H-5 manufactured by Rock Paint Co., Ltd. was used, and the thickness was about 3 μm. For the interface not labeled as an adhesive, the copper foil and the PET film are simply laminated. With respect to each electromagnetic shielding material, it installed in the magnetic field shielding effect evaluation apparatus (Techno Science Japan company type | model TSES-KEC), and evaluated the magnetic field shielding effect by the method similar to the test example 2. FIG.

  The results are shown in FIGS. It can be seen that when the metal foils are stacked, the magnetic field shielding effect is improved regardless of whether or not the PET film is stacked between the metal foils. And it turns out that a magnetic field shielding effect improves notably by laminating | stacking PET film between metal foil. Moreover, by comparing (g) and (f) in FIG. 7, it can be seen that the magnetic field shielding effect is enhanced even when the total thickness of the copper foil is small when laminating via a PET film. Further, when (b) and (f) are compared in FIG. 8, (b) shows a laminated structure of three copper foils (total thickness of copper foil 51 μm), whereas (f) shows two copper foils. Since the total thickness of copper foil was larger in (f), (b) showed an excellent magnetic field shielding effect. Further, when (b) and (e) are compared in FIG. 8, both have a laminated structure of three copper foils, and show almost the same shielding effect in the high frequency region, but each copper in the low frequency region. The magnetic field shielding effect of (e) with a large foil thickness was excellent. From FIG. 9, the magnetic field shielding effect by laminating | stacking 3 or more sheets similarly through a PET film similarly in aluminum foil can be confirmed.

  Table 2 shows the magnetic field shielding characteristics at 1 MHz for the test examples (a) to (m). In Test Example 3, (a), (b), (e), (i), (j), and (k) were able to achieve a magnetic field shield characteristic of 36 dB or more in the entire region of 1 MHz to 1000 MHz. )Met. In (a), the total thickness of the copper foil is only 68 μm, which is only about ¼ of the thickness of the 280 μm copper foil that achieved this characteristic in Test Example 2. In (j), the total thickness of the aluminum foil is only 90 μm, which is only 3/10 of the 300 μm aluminum foil that achieved the characteristics in Test Example 2. It can be seen that even if the weight of PET is taken into consideration, the weight can be significantly reduced. In (i) and (k), the target characteristics can be achieved, but the workability cannot be ensured because the thickness per metal foil is too large.

<Test Example 4: Verification of influence of σ _M × d _M × d _R on magnetic field shielding effect>
Each metal foil and insulating film described in Table 3 were prepared, and electromagnetic wave shielding materials of Test Examples 4-1 to 4-24 were prepared. Each symbol described in Table 3 indicates the following.
Cu: rolled copper foil (conductivity at 20 ° C .: 58.0 × 10 ⁶ S / m)
Al: Aluminum foil (conductivity at 20 ° C .: 39.6 × 10 ⁶ S / m)
Electrolytic Cu: electrolytic copper foil (conductivity at 20 ° C .: 56.0 × 10 ⁶ S / m)
Ni: nickel foil (conductivity at 20 ° C .: 14.5 × 10 ⁶ S / m)
Fe: soft iron foil (conductivity at 20 ° C .: 9.9 × 10 ⁶ S / m)
sus: stainless steel foil (conductivity at 20 ° C .: 1.4 × 10 ⁶ S / m)
PI: polyimide film (relative permittivity at 20 ° C .: 3.5)
PET: Polyethylene terephthalate film (relative permittivity at 20 ° C .: 3.0)
PTFE: polytetrafluoroethylene film (relative permittivity at 20 ° C .: 2.1)
PA: Polyamide film (relative permittivity at 20 ° C .: 6.0)
Air gap: Metal foils were separated by air (relative permittivity at 20 ° C .: 1.0)

(Test Examples 4-1 to 4-2: Magnetic shield effect of one metal foil)
With respect to the rolled copper foil (thickness: 150 μm) and the aluminum foil (thickness: 300 μm), the magnetic field shielding effect in a single layer was investigated. The prepared metal material was installed in a magnetic field shielding effect evaluation apparatus (Techno Science Japan Co., Ltd., model TSES-KEC), and the magnetic field shielding effect was evaluated by the KEC method at a frequency of 1 MHz and 20 ° C.

(Test Example 4-3: Magnetic field shielding effect when three metal foils are laminated)
Three rolled copper foils (thickness: 33 μm) were prepared, and these were simply laminated without using an adhesive, and installed in a magnetic field shielding effect evaluation device (Techno Science Japan Co., Ltd. Model TSES-KEC). The magnetic field shielding effect was evaluated by the same method as -1.

(Test Example 4-4: Magnetic field shielding effect when two metal foils are laminated via a resin film)
Using a polyethylene terephthalate (PET) film with a thickness of 250 μm as a resin film, a rolled copper foil with a thickness of 7 μm as a metal foil, and simply laminating without using an adhesive, the laminate structure shown in Table 3 is obtained. An electromagnetic shielding material was produced. This electromagnetic wave shielding material was installed in a magnetic field shielding effect evaluation apparatus (Techno Science Japan Co., Ltd. model TSES-KEC), and the magnetic field shielding effect was evaluated in the same manner as in Test Example 4-1.

(Test Example 4-5: Magnetic field shielding effect when two metal foils are laminated via a resin film)
By using a polyethylene terephthalate (PET) film having a thickness of 100 μm as a resin film, using a rolled copper foil having a thickness of 8 μm as a metal foil, and simply laminating without using an adhesive, the laminated structure shown in Table 3 is obtained. An electromagnetic shielding material was produced. This electromagnetic wave shielding material was installed in a magnetic field shielding effect evaluation apparatus (Techno Science Japan Co., Ltd. model TSES-KEC), and the magnetic field shielding effect was evaluated in the same manner as in Test Example 4-1.

(Test Example 4-6: Magnetic field shielding effect when two metal foils are installed via an air layer)
Air was used as the resin film, and aluminum foils with thicknesses of 6 μm and 30 μm were used as the metal foils, and electromagnetic wave shielding materials having a laminated structure shown in Table 3 were produced. In this example, the two aluminum foils were arranged in parallel at intervals of 50 μm in air with a copper plate having a large square opening at the center. This electromagnetic wave shielding material was installed in a magnetic field shielding effect evaluation apparatus (Techno Science Japan Co., Ltd. model TSES-KEC), and the magnetic field shielding effect was evaluated in the same manner as in Test Example 4-1.

(Test Example 4-7: Magnetic field shielding effect when three metal foils are laminated via a resin film: σ _M × d _M × d _R <3 × 10 ⁻³ )
An electromagnetic wave shield having the laminated structure shown in Table 3 by using a polyimide (PI) film having a thickness of 9 μm as a resin film, an aluminum foil having a thickness of 6 μm as a metal foil, and simply laminating without using an adhesive. A material was prepared. This electromagnetic wave shielding material was installed in a magnetic field shielding effect evaluation apparatus (Techno Science Japan Co., Ltd. model TSES-KEC), and the magnetic field shielding effect was evaluated in the same manner as in Test Example 4-1.

(Test Example 4-8)
By using a polyimide (PI) film with a thickness of 100 μm as a resin film, a rolled copper foil with a thickness of 17 μm as a metal foil, and simply laminating without using an adhesive, an electromagnetic wave having a laminated structure shown in Table 3 A shield material was produced. This electromagnetic wave shielding material was installed in a magnetic field shielding effect evaluation apparatus (Techno Science Japan Co., Ltd. model TSES-KEC), and the magnetic field shielding effect was evaluated in the same manner as in Test Example 4-1.

(Test Example 4-9)
By using a polyethylene terephthalate (PET) film having a thickness of 100 μm as a resin film, an aluminum foil having a thickness of 20 μm as a metal foil, and simply laminating without using an adhesive, an electromagnetic wave having a laminated structure shown in Table 3 A shield material was produced. This electromagnetic wave shielding material was installed in a magnetic field shielding effect evaluation apparatus (Techno Science Japan Co., Ltd. model TSES-KEC), and the magnetic field shielding effect was evaluated in the same manner as in Test Example 4-1.

(Test Example 4-10)
By using a polyethylene terephthalate (PET) film having a thickness of 100 μm as a resin film, an electrolytic copper foil having a thickness of 30 μm as a metal foil, and simply laminating without using an adhesive, it has a laminated structure shown in Table 3. An electromagnetic shielding material was produced. This electromagnetic wave shielding material was installed in a magnetic field shielding effect evaluation apparatus (Techno Science Japan Co., Ltd. model TSES-KEC), and the magnetic field shielding effect was evaluated in the same manner as in Test Example 4-1.

(Test Example 4-11)
An electromagnetic wave having a laminated structure shown in Table 3 is obtained by using a polyethylene terephthalate (PET) film having a thickness of 100 μm as a resin film, a nickel foil having a thickness of 50 μm as a metal foil, and simply laminating without using an adhesive. A shield material was produced. This electromagnetic wave shielding material was installed in a magnetic field shielding effect evaluation apparatus (Techno Science Japan Co., Ltd. model TSES-KEC), and the magnetic field shielding effect was evaluated in the same manner as in Test Example 4-1.

(Test Example 4-12)
By using a polyethylene terephthalate (PET) film having a thickness of 100 μm as a resin film, a soft iron foil having a thickness of 50 μm as a metal foil, and simply laminating without using an adhesive, an electromagnetic wave having a laminated structure described in Table 3 A shield material was produced. This electromagnetic wave shielding material was installed in a magnetic field shielding effect evaluation apparatus (Techno Science Japan Co., Ltd. model TSES-KEC), and the magnetic field shielding effect was evaluated in the same manner as in Test Example 4-1.

(Test Example 4-13)
By using a polytetrafluoroethylene (PTFE) film having a thickness of 500 μm as a resin film, a stainless steel foil having a thickness of 50 μm as a metal foil, and simply laminating without using an adhesive, the laminated structure shown in Table 3 is obtained. An electromagnetic wave shielding material having the same was produced. This electromagnetic wave shielding material was installed in a magnetic field shielding effect evaluation apparatus (Techno Science Japan Co., Ltd. model TSES-KEC), and the magnetic field shielding effect was evaluated in the same manner as in Test Example 4-1.

(Test Example 4-14)
Using a polyethylene terephthalate (PET) film having a thickness of 100 μm as a resin film, a rolled copper foil having a thickness of 6 μm as a metal foil, and simply laminating without using an adhesive, the laminate structure shown in Table 3 is obtained. An electromagnetic shielding material was produced. This electromagnetic wave shielding material was installed in a magnetic field shielding effect evaluation apparatus (Techno Science Japan Co., Ltd. model TSES-KEC), and the magnetic field shielding effect was evaluated in the same manner as in Test Example 4-1.

(Test Example 4-15)
Using a polyethylene terephthalate (PET) film having a thickness of 100 μm as a resin film, using a rolled copper foil having a thickness of 17 μm as a metal foil, and simply laminating without using an adhesive, the laminated structure shown in Table 3 is obtained. An electromagnetic shielding material was produced. This electromagnetic wave shielding material was installed in a magnetic field shielding effect evaluation apparatus (Techno Science Japan Co., Ltd. model TSES-KEC), and the magnetic field shielding effect was evaluated in the same manner as in Test Example 4-1.

(Test Example 4-16)
By using a polyethylene terephthalate (PET) film having a thickness of 100 μm as a resin film, a rolled copper foil having a thickness of 33 μm as a metal foil, and simply laminating without using an adhesive, the laminated structure shown in Table 3 is obtained. An electromagnetic shielding material was produced. This electromagnetic wave shielding material was installed in a magnetic field shielding effect evaluation apparatus (Techno Science Japan Co., Ltd. model TSES-KEC), and the magnetic field shielding effect was evaluated in the same manner as in Test Example 4-1.

(Test Example 4-17)
Using a polyethylene terephthalate (PET) film with a thickness of 9 μm as a resin film, using a rolled copper foil with a thickness of 7 μm and 33 μm as a metal foil, and simply laminating without using an adhesive, the laminated structure described in Table 3 An electromagnetic shielding material having a thickness of 10 was prepared. This electromagnetic wave shielding material was installed in a magnetic field shielding effect evaluation apparatus (Techno Science Japan Co., Ltd. model TSES-KEC), and the magnetic field shielding effect was evaluated in the same manner as in Test Example 4-1.

(Test Example 4-18)
By using a polyethylene terephthalate (PET) film having a thickness of 500 μm as a resin film, a rolled copper foil having a thickness of 17 μm as a metal foil, and simply laminating without using an adhesive, the laminated structure shown in Table 3 is obtained. An electromagnetic shielding material was produced. This electromagnetic wave shielding material was installed in a magnetic field shielding effect evaluation apparatus (Techno Science Japan Co., Ltd. model TSES-KEC), and the magnetic field shielding effect was evaluated in the same manner as in Test Example 4-1.

(Test Example 4-19)
Using a polytetrafluoroethylene (PTFE) film having a thickness of 100 μm as a resin film, using a rolled copper foil having a thickness of 17 μm as a metal foil, and simply laminating without using an adhesive, the laminated structure described in Table 3 An electromagnetic shielding material having a thickness of 10 was prepared. This electromagnetic wave shielding material was installed in a magnetic field shielding effect evaluation apparatus (Techno Science Japan Co., Ltd. model TSES-KEC), and the magnetic field shielding effect was evaluated in the same manner as in Test Example 4-1.

(Test Example 4-20)
An electromagnetic wave having a laminated structure shown in Table 3 is obtained by using a polyamide (PA) film having a thickness of 100 μm as a resin film, a rolled copper foil having a thickness of 17 μm as a metal foil, and simply laminating without using an adhesive. A shield material was produced. This electromagnetic wave shielding material was installed in a magnetic field shielding effect evaluation apparatus (Techno Science Japan Co., Ltd. model TSES-KEC), and the magnetic field shielding effect was evaluated in the same manner as in Test Example 4-1.

(Test Example 4-21)
Using a polyethylene terephthalate (PET) film having a thickness of 100 μm as a resin film, a rolled copper foil having a thickness of 33 μm and a nickel foil having a thickness of 30 μm as a metal foil, and simply laminating without using an adhesive, Table 3 An electromagnetic shielding material having the described laminated structure was produced. This electromagnetic wave shielding material was installed in a magnetic field shielding effect evaluation apparatus (Techno Science Japan Co., Ltd. model TSES-KEC), and the magnetic field shielding effect was evaluated in the same manner as in Test Example 4-1.

(Test Example 4-22)
By using a polyethylene terephthalate (PET) film having a thickness of 12 μm as the resin film, a rolled copper foil having a thickness of 12 μm and a rolled copper foil having a thickness of 17 μm as the metal foil, and simply laminating without using an adhesive, Table 3 An electromagnetic shielding material having the laminated structure described in 1 was produced. This electromagnetic wave shielding material was installed in a magnetic field shielding effect evaluation apparatus (Techno Science Japan Co., Ltd. model TSES-KEC), and the magnetic field shielding effect was evaluated in the same manner as in Test Example 4-1.

(Test Example 4-23)
By using a polyethylene terephthalate (PET) film having a thickness of 100 μm as a resin film, using a rolled copper foil having a thickness of 12 μm as a metal foil, and simply laminating without using an adhesive, the laminated structure shown in Table 3 is obtained. An electromagnetic shielding material was produced. This electromagnetic wave shielding material was installed in a magnetic field shielding effect evaluation apparatus (Techno Science Japan Co., Ltd. model TSES-KEC), and the magnetic field shielding effect was evaluated in the same manner as in Test Example 4-1.

(Test Example 4-24)
By using a polyethylene terephthalate (PET) film with a thickness of 9 μm as a resin film, an aluminum foil with a thickness of 20 μm as a metal foil, and simply laminating without using an adhesive, an electromagnetic wave having the laminated structure shown in Table 3 A shield material was produced. This electromagnetic wave shielding material was installed in a magnetic field shielding effect evaluation apparatus (Techno Science Japan Co., Ltd. model TSES-KEC), and the magnetic field shielding effect was evaluated in the same manner as in Test Example 4-1.

  In addition, in said evaluation, the electrical conductivity of metal foil was measured by the double-brich method of JISC2525: 1999. The relative dielectric constant was measured by the B method described in JIS C 2151: 2006.

The results are shown in Table 3. “Minimum σ _M d _M d _R ” in Table 3 is the metal foil and resin in which σ _M × d _M × d _R is the smallest among all combinations of metal foil and resin film used in each test example. Values for film combinations. As can be understood from the results of Test Examples 4-1 and 4-2, even if the thickness of the metal foil is more than 100 μm, the shielding effect is only about 31 to 33 dB. As can be understood from the results of Test Example 4-3, no significant improvement in the shielding effect is observed even when only the metal foil is laminated. As can be understood from the results of Test Examples 4-4 to 4-6, the same applies even when two metal foils are laminated via a resin film. Moreover, even when three metal foils are laminated via a resin film from the results of Test Example 4-7, it is understood that the improvement of the shielding effect is limited when σ _M × d _M × d _R is insufficient. .

On the other hand, three metal foils are laminated via a resin film, and σ _M × d _M × d _R is 3 × 10 ⁻³ or more for all combinations of the metal foil and the resin film 4-8 to In 4-24, it can be understood that the shielding effect is remarkably excellent. For example, in contrast to Test Example 4-1, which required a thickness of 150 μm to obtain a shield effect of 31.1 dB with one copper foil, Test Example 4-8 has a copper foil having a thickness of about 1/3. Although it is only used, the shielding effect is improved by about 26 dB. Further, in contrast to Test Example 4-2 in which a thickness of 300 μm was necessary to obtain a shielding effect of 33.1 dB with one aluminum foil, in Test Example 4-9, only an aluminum foil having a thickness of 1/5 was used. Even though it is not used, the shielding effect is improved by about 19 dB.

It can also be understood that the higher the minimum σ _M d _M d _R in the combination of the metal foil and the resin film, the higher shielding effect can be obtained while reducing the total thickness of the metal foil. For example, in all of Test Examples 4-18 to 4-20, the total thickness of the copper foil is 51 μm, but it can be seen that there is a large difference in the shielding effect due to the difference in the minimum σ _M d _M d _R.

DESCRIPTION OF SYMBOLS 11 Electromagnetic shielding material 12 Preform metal mold 13 Electromagnetic wave shielding material 14 Injection mold 15 Integrated molding 21 Electromagnetic wave shielding material 22 Injection mold 22a First mold (upper mold)
22b Second mold (lower mold)
23 Injection port 25 Integrated molded product

Claims (22)

  An electromagnetic wave shielding case comprising a resin case main body and an electromagnetic wave shielding material for bonding and covering an inner surface and / or an outer surface of the resin case main body, wherein the electromagnetic wave shielding material includes at least one metal foil and at least one metal foil. An electromagnetic wave shielding casing having a multilayer structure in which a plurality of resin films are closely laminated, and an electromagnetic shielding material layer forming a bonding surface with the inner surface and / or outer surface of the resin casing body is made of a resin film. body.   The electromagnetic shielding casing according to claim 1, wherein the metal foil and the resin film constituting the electromagnetic shielding material are closely laminated by thermocompression bonding.   The layer of the electromagnetic wave shielding material that forms the joint surface with the inner surface and / or the outer surface of the resin casing body is made of a resin film made of the same type of resin material as the resin casing body. The electromagnetic shielding housing described in 1.   The melting point of the resin constituting the resin film that is a layer of the electromagnetic wave shielding material that forms the joint surface with the inner surface and / or the outer surface of the resin casing body is ± with respect to the melting point of the resin constituting the resin casing body. The electromagnetic wave shielding casing according to any one of claims 1 to 3, wherein the electromagnetic shielding casing is within 5 ° C.   The electromagnetic shielding housing according to any one of claims 1 to 4, wherein the metal foil and the resin film constituting the electromagnetic shielding material are not broken.   The electromagnetic wave shielding material according to any one of claims 1 to 5, wherein the electromagnetic wave shielding material has a structure in which at least two metal foils are laminated via a resin film. The electromagnetic shielding casing according to any one of claims 1 to 6, wherein all combinations of the metal foil and the resin film constituting the electromagnetic shielding material satisfy σ _M × d _M × d _R ≧ 3 × 10 ^−3. .
However, the symbol in a formula shows the following.
σ _M : conductivity of metal foil at 20 ° C. (S / m)
d _M : Metal foil thickness (m)
d _R : thickness of resin film (m) The electromagnetic shielding casing according to any one of claims 1 to 7, wherein each metal foil constituting the electromagnetic shielding material has an electric conductivity at 20 ° C of 1.0 x 10 ⁶ S / m or more.   The thickness of each metal foil which comprises an electromagnetic wave shielding material is 4-50 micrometers, The electromagnetic wave shielding housing | casing as described in any one of Claims 1-8.   The electromagnetic wave shielding casing according to any one of claims 1 to 9, wherein each resin film constituting the electromagnetic wave shielding material has a relative dielectric constant at 20 ° C of 2.0 to 10.0.   The thickness of each resin film which comprises an electromagnetic wave shielding material is 4-500 micrometers, The electromagnetic wave shielding housing | casing as described in any one of Claims 1-10.   The electromagnetic shielding housing according to any one of claims 1 to 11, wherein the thickness of the thinnest portion of the resin housing body is 0.5 mm or more. A method for manufacturing an electromagnetic shielding casing comprising a resin casing main body and an electromagnetic shielding material for bonding and covering the inner surface and / or outer surface of the resin casing main body,
It has a multilayer structure in which at least one metal foil and at least one resin film are laminated, and at least one outermost layer is a resin film, and a film-like electromagnetic shielding material is set in a preform mold, A step of obtaining an electromagnetic wave shielding material preformed into a three-dimensional shape by pressure forming or vacuum forming;
In a state where the preformed electromagnetic wave shielding material is fitted into an injection mold having a cavity surface matching the three-dimensional shape of the electromagnetic wave shielding material so that the resin film forming the outermost layer is exposed in the cavity. Injecting the molten resin for the housing into the cavity of the injection mold, and solidifying by cooling, thereby integrating the preformed electromagnetic shielding material and the housing;
Manufacturing method.   The manufacturing method according to claim 13, wherein the resin film that forms the outermost layer and is exposed in the cavity is made of the same type of resin material as the resin casing body.   The manufacturing method according to claim 13 or 14, wherein the electromagnetic shielding housing is the electromagnetic shielding housing according to any one of claims 1 to 12.   In the process of obtaining the electromagnetic shielding material preformed into a three-dimensional shape, all the resin films constituting the electromagnetic shielding material are subjected to pressure forming and vacuum forming in a state where the heat deformation temperature of the resin film is higher than 20 ° C. Or the manufacturing method as described in any one of Claims 13-15 which press-molds.   In the process of integrating the preformed electromagnetic shielding material and the housing, a molten resin having a temperature exceeding the melting point of the injected resin by 5 ° C. or more and a temperature exceeding the melting point of the injected resin by 100 ° C. or less is injected. The manufacturing method according to any one of claims 13 to 16.   The manufacturing method according to any one of claims 13 to 17, wherein the pressure reduction molding or the vacuum molding is performed at a thickness reduction rate of 16% or more of the electromagnetic shielding material. A method for manufacturing an electromagnetic shielding casing comprising a resin casing main body and an electromagnetic shielding material for bonding and covering the inner surface and / or outer surface of the resin casing main body,
A film-like electromagnetic shielding material having a multilayer structure in which at least one metal foil and at least one resin film are laminated, and at least one outermost layer being a resin film, defines a three-dimensional shape of the electromagnetic shielding material A molten resin injection port in which a resin film for forming an outermost layer is installed in a second mold in an injection mold having a first mold having projections and depressions and a second mold having an injection port And the process of setting to face each other,
A step of obtaining a preformed electromagnetic wave shielding material by moving both molds to the position at the time of injection molding;
By injecting molten resin for the housing from the injection port provided in the second mold, the electromagnetic shielding material is made to follow the unevenness of the first mold by injection pressure, and then cooled and solidified. Integrating the molded electromagnetic shielding material and the housing;
Manufacturing method.   The manufacturing method according to claim 19, wherein the resin film that forms the outermost layer and faces the injection port is made of the same type of resin material as the resin casing body.   The manufacturing method according to claim 19 or 20, wherein the electromagnetic shielding housing is the electromagnetic shielding housing according to any one of claims 1 to 12.   The manufacturing method according to any one of claims 19 to 21, wherein the total thickness reduction rate of the electromagnetic shielding material in the preliminary molding and the main molding is set to 16% or more.