JPH0211038B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing electromagnetic shielding components, and particularly to a method for manufacturing electromagnetic shielding components that have a beautiful appearance and whose surfaces can be easily painted, plated, etc. .

In recent years, interference with other devices caused by electromagnetic waves generated by electronic devices such as computers, electronic games, video games, electronic cash registers, word processors, and calculators, such as malfunctions and stoppages, has become a problem. The necessity of taking some kind of legal measures against such electromagnetic interference is being considered.

Incidentally, the housings of electronic devices such as the above-mentioned OA-related devices are mostly made of plastic, but the electromagnetic interference described above cannot be prevented with conventional plastics.
Of course, countermeasures against electromagnetic interference should basically be taken through the circuit design of electronic devices, but it is difficult to sufficiently prevent electromagnetic wave radiation by that alone, and ultimately these devices The casing must shield electromagnetic waves and prevent them from being radiated to the outside, and this has created the need to provide electromagnetic shielding properties by making plastic conductive.

Broadly speaking, there are two possible methods for imparting electromagnetic shielding properties to plastics.
In other words, (a) a method of forming a conductive layer of metal or the like on the surface of a plastic molded product, and (b) a method of making the resin itself conductive by blending a conductive filler such as metal fiber with the resin. However, the former requires pretreatment in order to maintain good adhesion between the plastic and the coating material under the usage environment, and has the disadvantage of being relatively expensive.
On the other hand, the latter method has attracted attention in recent years as resin materials blended with conductive fillers such as aluminum, brass, and conductive carbon have become commercially available. When molding is used to obtain the housing of the electronic device, fillers, etc. naturally appear on the surface, making it impossible to obtain a molded product with a beautiful appearance. Due to the conductive filler, the surface becomes rough and there is a problem that effective surface coating treatment such as painting or plating cannot be applied.
Furthermore, if the end face of the filler material, such as metal fiber, is left as it is, which is exposed on the surface of the molded product, it may cause safety problems such as injury to the person handling the electronic equipment. There is also the inherent problem of damaging peripheral devices due to contact with them.

The present invention has been made in view of the above circumstances, and its purpose is to maintain effective electromagnetic shielding properties while maintaining a beautiful appearance and similar to conventional plastic products. It is an object of the present invention to provide a method for manufacturing electromagnetic shielding parts that can be easily subjected to surface coating treatments such as painting and plating.

In order to achieve this objective, the present invention uses such electromagnetic shielding components as
It is composed of a sandwich molded product having a core layer inside and a skin layer on the outside, and the core layer is made of a conductive resin material mixed with a predetermined conductive filler. In addition, in order to manufacture such electromagnetic shielding parts, a resin material that does not contain a conductive filler is injected as a skin layer forming material into a mold to be molded from a first injection device, and then Then, from the second injection device, a resin material mixed with a predetermined conductive filler is injected as a core layer forming material, so that the core layer is located inside the previously injected resin material that does not contain the conductive filler. Thus, a conductive resin material containing a conductive filler material is present.

As described above, according to the present invention, the resin mixed with a conductive filler, the so-called conductive resin material, is sealed inside, and the outside is made of only ordinary resin material. Because of the way it is formed, it can be made to have a beautiful appearance similar to conventional molded products, and of course there are coatings and coatings that are effective for achieving such a beautiful appearance.
It has become possible to perform treatments such as plating, and such electromagnetic shielding parts can be advantageously manufactured using the known sandwich molding method. In other words, the characteristics of the Sanderch molding method can be most effectively exhibited when producing an electromagnetic shielding component in which a conductive resin is disposed inside.

Here, the conductive resin material forming the core layer used in the present invention includes steel, stainless steel,
A predetermined amount, e.g., several vol% to several tens of vol. It is a resin material made conductive by mixing approximately vol% of the resin material, and the base resin of such a resin material is a known thermoplastic resin such as nylon, ABS resin, or polyolefin resin.

On the other hand, the resin material forming the skin layer is a normal thermoplastic resin (nylon, ABS resin, polyolefin resin, etc.) and does not contain any conductive filler like the conductive resin forming the core layer. It is something.

In order to manufacture the electromagnetic shielding component according to the present invention using such a conductive resin and a normal resin, a normal sandwich molding method is adopted, an example of which is shown in FIG. ing.

First, in FIG. 1, 2 is a mold consisting of a normal fixed mold and a movable mold, and inside the mold 2,
A product cavity is provided for molding the intended electromagnetic shielding component. Further, the injection device is composed of a first injection device 4 and a second injection device 6, and the normal resin material 8 for forming the skin layer injected from the first injection device 4 is fed by a valve 10. It is guided under control to the injection head 12 at the tip of the second injection device 6 and is injected into the mold 2. Further, the conductive resin 14 injected from the second injection device 6 is injected into the mold 2 from the injection head 12 under the control of a valve 16. Note that various structures are known as devices for performing such sanderch forming, and in the case of forming the sanderch in accordance with the present invention, devices of various known structures may be selected as appropriate. , will be used.

When manufacturing the electromagnetic shielding component according to the present invention using such a sandwich molding machine, first, the first injection device 4 injects a normal resin material (for example, ABS resin) for forming the skin layer.
8 is injected into the mold 2. When the normal resin material 8 as this skin layer is injected into the mold 2, the material 8 in the part that is in contact with the mold surface first cools and solidifies, and this solidified film acts as a heat insulator. From keeping the internal material in a molten state,
Next, a conductive resin material (e.g., mixed with 15 vol% brass fiber) is injected from the second injection device 6.
ABS resin) 14 is guided into the mold 2 and passes through the heat insulating film, thereby forming a sandwich molded product with a core layer made of the conductive resin material 14 inside. is obtained.

As described above, Sanderch molding is a molding method that makes good use of the flow characteristics of the molten material 8 in the mold 2, that is, the skin insulation effect, and because the material 8 injected first and the material 14 injected later are different. In addition, the skin layer and the core layer form a sandwich-like structure, and in the present invention, the conductive resin material 14 is used as the material for forming the core layer. Conductive resin material 14
Thus, a molded article in which is sealed inside can be advantageously obtained.

Incidentally, FIG. 2 shows an example of an electromagnetic shielding component (here, a solenoid cover) obtained according to the Sanderch molding method.
In FIG. 2, 20 is a skin layer made of the above-mentioned ordinary resin material 8, and while covered with this skin layer 20, a core layer 22 made of the above-mentioned conductive resin material 14 is formed inside the skin layer 20. It is being done.

Therefore, in the case of a sandwich molded product having such a structure, the skin layer 20 constituting the outer surface
However, since it is made of a normal resin material 8, its appearance (surface) can be made extremely beautiful, and the conductive filler is not exposed to the surface or protrudes from the surface. Therefore, the surface can be suitably subjected to surface coating treatments such as ordinary painting or plating.
Since the internal core layer 22 is formed of the conductive resin material 14, it has an effective shielding effect against electromagnetic waves that pass through the molded product. That is, within the core layer 22, conductive fillers such as metal fibers filled in the resin material 14 constituting the core layer 22 come into contact with each other to form a stable current conduction path, thereby shielding the transmission of electromagnetic waves. Therefore, it can be used as an effective electromagnetic shielding component.

Therefore, such Sanderchich molded products can be advantageously used as electromagnetic shielding parts in casings that cover electronic devices that emit electromagnetic waves, as well as shielding parts or covers that cover those electromagnetic wave emitting parts. In such use, the conductive filler does not protrude from the surface, which may cause injury to the operator or damage to the other party due to contact with peripheral equipment. Not at all. In addition,
When such an electromagnetic shielding sandwich molded product is attached to a predetermined electronic device, it is grounded in the same way as conventional shielding parts, but such grounding is done to the core layer 22.

As described above, a sanderch molded product with a core layer made of conductive resin material has excellent characteristics as an electromagnetic wave shielding component, but such a sanderch molded product also has the potential to be charged due to the conductivity of its core layer. It can also be suitably used as a prevention component. Therefore, when used as an antistatic component, it is desirable that the skin layer be as thin as possible in order to effectively guide static electricity to the core layer.

Although specific examples of the present invention have been described above,
The present invention is by no means to be construed as being limited only to these specific examples, and the sanderch molding machine to be used and the sanderch molding method to be employed may be appropriately selected from various known devices or methods. Furthermore, the shape of the sandwich molded product can be changed as appropriate depending on the shape of the electronic device to be shielded from electromagnetic waves. In short, without departing from the spirit of the present invention, various changes, modifications, improvements, etc. can be made to the present invention based on the knowledge of those skilled in the art, and such embodiments are also included in the present invention. It goes without saying that the invention falls within its scope.

As described above, the present invention uses a sanderch molded product in which a conductive resin material is sealed in the core layer by the sanderch molding method as an electromagnetic wave shielding component, thereby making the appearance similar to that of a normal molded product. It was possible to create something beautiful,
Furthermore, because of its smooth surface, it has the advantage of being able to be subjected to surface treatments such as painting and plating, and has great industrial significance as it can be advantageously used as electromagnetic shielding parts.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional explanatory diagram of a main part showing an example of a sand german molding machine for manufacturing an electromagnetic shielding component according to the present invention, and FIG. 2 is a cross-sectional view showing an example of an electromagnetic shielding component according to the present invention. . 2: Mold, 4: First injection device, 6: Second injection device, 8: Ordinary resin material, 10, 16: Valve, 12: Injection head, 14: Conductive resin material,
20: skin layer, 22: core layer.

Claims (1)

[Claims] 1. Inject a resin material that does not contain a conductive filler as a skin layer forming material from a first injection device into a mold in which the intended electromagnetic shielding component is to be molded;
Next, by injecting a conductive resin material mixed with a predetermined conductive filler as a core layer forming material from a second injection device, a core layer made of the conductive resin material is formed inside, and the conductive resin material is formed outside the core layer. 1. A method for producing an electromagnetic shielding part by the Sanderutsch molding method, which comprises forming a Sanderutsch molded product integrally having a skin layer made of a resin material that does not contain a filler.