JP2741400B2 - Method for producing sheet molding for electromagnetic wave shielding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Purpose of the Invention><Industrial application fields> The present invention prevents accidents, malfunctions, etc. due to electromagnetic noise by being fitted in the casing of various electronic devices or used as a casing itself. A method for producing a sheet molded body for electromagnetic wave shielding.

<Background of the Invention> In recent years, electronic devices using digital circuits have been rapidly penetrating into workplaces and homes. Of course, electronic devices are used everywhere, including not only at work and home, but also outdoors, such as automobiles, airplanes, trains, and communication facilities.
Plastics that are lightweight, have excellent workability and durability, and are inexpensive are often used for casings of these electronic devices, also for the purpose of insulation.

However, plastics are inherently highly transparent to electromagnetic waves, so high-frequency pulses generated by a large number of built-in ICs and LSIs radiate electromagnetic wave noise out of the casing. Malfunctions, malfunctions of various automatic control devices, and the like. In addition, so-called electromagnetic wave disturbances occur in which electronic circuits incorporated therein also malfunction due to intrusion of electromagnetic noise from other electronic devices. In addition to the adverse effects of this electromagnetic noise, plastic casings are easily charged with static electricity due to their high insulation properties.
The noise generated when the static electricity is discharged also causes a malfunction or directly destroys the electronic element.

By the way, in order to protect electronic devices and electronic circuits from these electromagnetic noises and electrostatic noises, it is conceivable to solve the problem by imparting conductivity to plastic as a casing.

For this reason, conventionally, in addition to the primary processing of mixing various conductive fillers such as carbon black at the plastic raw material stage, as a secondary processing, a conductive paint mixed with silver fine particles or the like is applied. Various methods have been tried, such as thermal spraying of metal, vacuum deposition, sputtering, ion plating, etc. of aluminum or the like, electroless plating, electroplating, spray plating, and attaching metal foil such as aluminum foil.

However, mixing a conductive filler at the raw material stage of plastics causes problems such as increased cost and reduced moldability.In addition, conductive paint application, metal spraying, vacuum deposition, plating, etc. There is also a fear of accidents such as the separation of a part of them and short circuit.

<Technical items that we have attempted to develop> As described above, the methods that have been tried in the past may partially impair the reliability of the internal insulation, and each requires special processing. However, it lacks versatility such as later processing. The present invention has been made in view of such a background, and a part that performs an electromagnetic wave shielding function is finished as an independent member, that is, a sheet molded body. By carrying it, it is possible to demonstrate the electromagnetic wave shielding property, and also to ensure the insulation of the surface, and to fit inside the existing casing,
An attempt was made to develop a new method for easily obtaining a sheet molded body for electromagnetic wave shielding which could be used as a casing itself.

<< Constitution of the Invention >><Means for Achieving the Object> The method for producing a sheet molded body for electromagnetic wave shielding according to the first invention of the present application is a method of winding a long metal thin film into a coil-shaped material, After turning the end face of the material to obtain a thin and long metal fiber, disperse the thin and long metal fiber into a mat of appropriate width, and attach a synthetic resin film to the mat-shaped metal fiber from above and below. Thus, a sheet material in which the metal fibers are sandwiched between synthetic resin films is obtained, and the sheet material is heated and softened, brought into close contact with a mold by vacuum pressure and / or compressed air pressure, and then cooled and solidified. It is characterized by shaping.

Further, the method of manufacturing a sheet molded body for electromagnetic wave shielding according to the second invention according to the present application is to disperse thin and long metal fibers into a mat having an appropriate width, and then to form at least one of the mat-shaped metal fibers. A non-woven fabric made of synthetic resin fibers is layered, and the two are needle-punched to entangle the fibers with each other, and further, a synthetic resin film is layered from above and below, and the metal fibers are interposed between the synthetic resin films. Is obtained by sandwiching the sheet material, and the sheet material is heated and softened, brought into close contact with a mold by vacuum pressure and / or compressed air pressure, and then cooled and solidified to form the sheet material. .

Furthermore, in addition to the above requirements, the method for manufacturing a sheet molded body for electromagnetic wave shielding according to the third invention according to the present application further includes a step of applying a synthetic resin film to a mat-shaped metal fiber from above and below. A plastic material is used, and the synthetic resin films are melt-bonded to each other with a heat roll to obtain the sheet material.

The present invention aims to achieve the above object.

<< Effect of the Invention >> Since the molded article obtained by the production method of the present invention supports the metal fibers in a sandwich shape between the synthetic resin films, the insulating properties of the surface are secured by the upper and lower synthetic resin films. Above, the conductivity of the metal fibers spread over the entire surface of the intermediate layer prevents electromagnetic waves from leaking out or entering from outside.

In addition, the metal fibers supported between the synthetic resin films,
Since it is a long fiber, there is little possibility that the fiber will penetrate through the synthetic resin film covering the fiber, so that the surface insulation of the synthetic resin film can be ensured. Further, after the whole is formed into a relatively thin one-leaf sheet material, it is formed by so-called thermoforming, so that it can be fitted inside a relatively complicated casing or used as a casing itself.

According to the method of the present invention, such a sheet molding for electromagnetic wave shielding can be easily obtained. Further, according to the first invention, a thin long metal fiber can be easily and inexpensively obtained, so that the present electromagnetic wave shielding sheet molded article can also be manufactured at low cost. Further, according to the second invention, a product having further enhanced surface insulation properties can be obtained.

<Example> Fig. 1 shows an example A of an electromagnetic wave shielding sheet molded body according to the present invention, which is formed into a deformed rectangular ship bottom shape obtained by a so-called vacuum molding method. In the same figure, this is drawn in a prone state.

Therefore, until the sheet material 1 as the material is obtained,
The process until this is formed into the same shape will be described separately with reference to FIGS. 2 and 3. In addition, the sheet forming body A for electromagnetic wave shielding itself will be appropriately described in the meantime.

FIG. 2 and FIG. 3 show a schematic flow of one embodiment of the second invention. FIG. 2 shows a sheet material 1 as a raw material capable of exhibiting an electromagnetic wave shielding action at the front stage thereof. FIG. 3 shows the subsequent stage, until the sheet material 1 is formed into the shape as shown in FIG.

In FIG. 2, reference numeral 1 denotes a sheet material as a material for electromagnetic wave shielding before being formed into a shape as shown in FIG. 1, reference numeral 21 denotes a metal long fiber as a raw material, and reference numeral 2 denotes a mat having an appropriate width by dispersing it. It shows the state arranged in the shape, 3
Is a nonwoven fabric made of polypropylene fibers 31 supported in a roll 32 state above this mat-shaped metal long fiber,
4, 4 are soft vinyl chloride films which are also supported slightly above and below the rolls 41, 41, respectively, and 5, 5 are heat rolls which are supported further close to each other at the further front thereof, and 6 are needles. A base on which a punch needle 61 is implanted and which is vertically moved by a separate driving means.

In such an approximate arrangement, metal filaments
21 is a mat having an appropriate width, which is firstly raked by a conventionally known means (not shown), for example, a rake-shaped hooking member, passing between rolls and weirs, and uniformly dispersed with a substantially uniform thickness. It is sent forward in two forms.

In this embodiment, the metal long fiber 21 includes
The brass material is used, and in order to make it a long fiber, first, a long brass thin film is wound tightly into a coil-shaped material, and then this end face is applied at once as appropriate. It is machined with a byte. That is, a long fiber having a cross section of the width of the material thickness of the metal thin film and the width of the feed during turning can be obtained. This method is exactly the first step in the first invention, and if the long metal fiber 21 thus obtained is used,
It can be obtained as a thin, long and flexible fiber, and also as a fiber with less burr. It is advantageous in handling, for example, arranging in a mat shape, and is also a sheet material as an electromagnetic wave shielding material, and an electromagnetic wave shielding material. Even in the finished state of the sheet molded body, each end of the metal fiber rarely penetrates through the layer of the synthetic resin film and jumps out. The thickness of the metal thin film in this case depends on the material and hardness of the metal, but is from several μm to several hundred μm, preferably
0μ is appropriate. Of course, it depends on various conditions such as a cutting speed, a feed speed, a cutting width, a rake angle of a cutting tool and the like, and by adjusting these conditions, an optimum long metal fiber can be obtained.

Then, such a metal long fiber 21 is used as a mat 2 having an appropriate width.
After being formed, the non-woven fabric 3 of the polypropylene fiber 31 is piled up on the mat 2 of the long metal fiber 21 while being unwound from the upper roll 32, and subsequently, the needle punch base 6 located above these is placed. Moves up and down, and the metal long fibers and the nonwoven fabric fibers are entangled by the needles 61 implanted therein.

Here, the reason why the nonwoven fabric 3 of the polypropylene fiber 31 is overlapped and entangled with the nonwoven fabric 3 is to provide a temporary fixing meaning of the long metal fiber 21, to facilitate the transportation of the process, to enhance insulation after finishing, and the like. . Further, as the material of the fiber of the nonwoven fabric, a material having a higher softening and melting point than the material of the synthetic resin film to be subsequently laminated is advantageous in heat-welding the upper and lower synthetic resin films to be described later with a heat roll or the like. It is.

Subsequently, films 4, 4 of soft vinyl chloride are unwound from the upper and lower rolls 41, 41, and both films 4, 4 are now integrated mat 7 of metal filament 21 and polypropylene 31 entangled. , And immediately thereafter, it is passed between the heat rolls 5, 5.

The heat rolls 5 and 5 are heated by heating means (not shown), and the vinyl chloride film 4 passing therethrough
4 is appropriately softened and melted, and both fibers of the integrated mat 7 are
By applying pressure so as to be melted between the portions 21 and 31, the integrated mat 7 is laminated with the soft vinyl chloride films 4 and 4 from above and below in a sandwich manner.
In the above, in the present embodiment, the metal filaments having a wire diameter of 30 μ × 50 μ are dispersed such that at least 7,8 of the filaments overlap and at least 2 mm square has one metal filament, and 500 μm. The film was made of vinyl chloride and used for upper and lower layers.

The thus obtained sheet material 1 as an electromagnetic wave shielding material has a thickness of about 1 mm, and thin and long brass fibers 21 arranged in a mat form are used as intermediate layers of the vinyl chloride films 4 and 4. It is held in a sandwich shape and is itself a single flexible sheet material.

Here, the reason why soft vinyl chloride was used for the films 4 and 4 was that the softening and melting point was low and the efficiency of this laminating work was good, and that the completed sheet material 1 for the electromagnetic wave shielding was also flexible. Is obtained, and the next molding becomes easy.

Subsequently, the sheet material 1 is so-called thermoformed. In the example, the same thermoforming was performed by vacuum forming. That is, FIGS. 3A to 3C schematically show a process of thermoforming by a vacuum forming machine.
The four sides are clamped and fixed to a support frame 81, which is heated and softened by a heater 82 (the state shown in FIG. 2 (a)), and then set on a mold 9 (see FIG. 2 (b)). Status)
Then, the space 90 formed by the softened sheet material 1 and the molding die 9 is evacuated and evacuated, and the softened sheet material 1 is deformed and adhered to the molding die 9 as shown in FIG. (C)), and then, after being cooled by cold air or the like and fixed in shape, it is taken out of the mold 9. At this time, the sheet material 1 is deformed and stretched in a manner similar to the molding die 9, but since the metal long fibers 21 carried on the intermediate layer are thin and long, the degree of freedom of deformation is high, and the sheet material 1 must have an extreme shape. For example, the deformation conforming to the shape of the mold 9 is performed. Here, by adjusting the thickness, hardness and the like of the synthetic resin film, it is possible to form a considerably deep shape.

As described above, according to the present method, the electromagnetic wave shielding sheet molded article A can be obtained in a very simple process, so that the electromagnetic wave shielding sheet molded article A is fitted into the inside of the casing of the electronic device, or the electromagnetic wave shielding sheet molded article A itself can be obtained. Is used as a casing, the long and thin metal fibers arranged in a mat form impart conductivity to the inside of the casing, and an electromagnetic wave shielding effect is produced.

And use it as a casing. In any case, since the front and back surfaces of the sheet for electromagnetic wave shielding show the surfaces of the vinyl chloride film, the inner surface of the casing is insulated and the danger of a short circuit accident is reduced. This means that there is little danger of short-circuiting, not only when the electronic board vibrates or moves, and the substrate contact and the inner surface of the casing come into contact with each other, but also when the present electromagnetic wave shielding sheet molded article separates from the inner surface of the casing. This is also advantageous over the prior art. Of course, if it is formed in the same shape as the inner surface of the casing, there is no danger of peeling and falling.

In addition, the plastic casing of the electronic device is not limited to a box-type one, but also includes a complicated molded body in a child toy or the like to which the application of a digital circuit will be further advanced in the future. Instead of being applied to a small casing, it can be shaped like a tent and used as a computer room, control room, or the like.

Further, in the above embodiment, a brass material was used as the long metal fiber, and in obtaining this,
First, a long brass thin film was firmly wound into a coil-shaped body, and then this end face was turned to obtain a conductive material such as stainless steel, aluminum, iron, or copper. Also,
Of course, it can be applied in the same manner, and it is not necessary that the thin film be obtained by cutting from a wound coil-like body. Good.

Further, the fiber length is desirably about several cm to several tens of cm, or more, and the degree of dispersion is the required performance as a molded sheet for electromagnetic wave shielding,
That is, it may be determined according to the magnitude of the static electricity removal and the electromagnetic wave shielding effect. Further, in the above embodiment, the nonwoven fabric of the polypropylene fiber was overlapped with the long metal fiber,
It is not always necessary to overlap, and a synthetic resin film may be applied only to the long metal fiber. Further, the material itself of the nonwoven fabric is not limited to polypropylene fibers, but may be various synthetic fibers such as polyester and polyurethane.

Further, in the above embodiment, a thermoplastic resin film was used to join the two synthetic resin films, and this was thermally welded with a heat roll. However, the present invention is not limited to this, and a separate hot melt film was sandwiched. Heat welding with
Needless to say, a film having adhesiveness on both sides may be put in and pressure-bonded thereto, a synthetic resin film having an adhesive surface may be superimposed, or pressure-bonded while applying an adhesive.

Furthermore, the synthetic resin film is not limited to a soft vinyl chloride film, but may be acrylonitrile / butadiene /
Various thermoplastic resins such as styrene resin (ABS), acrylic resin (PMMA), and polystyrene resin (PS) can be used. In addition, when the sheet material is thermoformed, in addition to the straight forming of the embodiment, Drape forming, plug assist forming, reverse draw forming, plug assist reverse draw forming, or even using a compressed air forming machine and using compressed air instead of vacuum.

<< Effects of the Invention >> As described above, according to the method of the present invention, it is possible to impart conductivity to a casing or the like of an electronic device in an extremely simple process, and to provide an electromagnetic wave shielding effect. The sheet molded body can be obtained, and the sheet molded body for electromagnetic wave shielding obtained by the manufacturing method of the present invention is an independent member itself, and although it imparts electromagnetic wave shielding properties, its surface has insulating properties. Therefore, it can be used as a casing as it is. Therefore, the present invention can greatly contribute to solving the problem of electromagnetic noise of electronic devices, which is now a major social problem.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a state in which the sheet is formed into a deformed rectangular ship bottom mold by the method of manufacturing an electromagnetic wave shielding sheet molded article of the present invention, and FIG. FIGS. 3 (a), 3 (b) and 3 (c) are schematic views showing the basic flow of one embodiment of the process of thermoforming this sheet material by a vacuum forming machine. DESCRIPTION OF SYMBOLS 1 ... Sheet material for electromagnetic wave shielding 2 ... Mat-shaped long metal fiber, 21 ... Metal long fiber 3 ... Non-woven fabric, 31 ... Polypropylene fiber 4.4: Soft vinyl chloride film 5.5: Heat Roll 61: Needle for needle punch 9: Mold

Claims (3)

(57) [Claims] 1. A long metal thin film is wound into a coil-shaped material, and the end surface of the coil-shaped material is turned to obtain a thin long metal fiber. A sheet having a width of mat, a synthetic resin film is laid on the mat-shaped metal fiber from above and below to obtain a sheet material in which the metal fiber is sandwiched between synthetic resin films, and the sheet material is heated. Soften, vacuum pressure and / or
Alternatively, a method for producing a sheet molded body for electromagnetic wave shielding, characterized in that the molded body is brought into close contact with a mold by compressed air pressure and then cooled and solidified to form the molded body. 2. A method in which thin and long metal fibers are dispersed to form a mat having an appropriate width, and a nonwoven fabric made of a synthetic resin fiber is laminated on at least one of the mat-shaped metal fibers, and both are needle-punched. Then, the fibers are entangled with each other, and further, a synthetic resin film is layered from above and below to obtain a sheet material in which the metal fibers are sandwiched between synthetic resin films, and the sheet material is A method for producing a sheet molded body for electromagnetic wave shielding, wherein the molded article is heated and softened, adhered to a mold under vacuum pressure and / or compressed air pressure, and then cooled and solidified. 3. A method of laminating a synthetic resin film on a mat-shaped metal fiber from above and below, using a thermoplastic synthetic resin film and fusing and bonding the synthetic resin films to each other with a heat roll. The method for producing a sheet molded body for electromagnetic wave shielding according to claim 1 or 2, wherein a material is obtained.