JPH0425852B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of manufacturing a plastic molded article capable of shielding electromagnetic waves.

Conventional Technology Cases for electronic devices made of plastic molded products, such as housing cases for personal computers, are susceptible to electromagnetic waves from the outside affecting the electronic devices inside the case, or conversely, electromagnetic waves generated from the electronic devices inside the case. Electromagnetic wave shielding properties are required to prevent electromagnetic waves from being emitted to the outside.

Conventional methods for shielding electromagnetic waves in this type of case include painting the inner or outer surface of the case with electromagnetic wave-shielding paint, or mixing fine electromagnetic wave-shielding filler into the plastic used to mold the case. There are materials in which electromagnetic wave shielding properties are imparted to the material itself (for example, JP-A-59-204300 and JP-A-60-13516).

Problems to be Solved by the Invention The former method of painting in the above-mentioned conventional technique creates a poor working environment due to the scattering of paint particles caused by spraying, and brush painting, which is performed in such a way, produces a poor finish and is inefficient. Furthermore, there was a problem in that the paint peeled off during use of the case, adversely affecting the stored items.

On the other hand, when using the latter mixed material, the electromagnetic shielding filler to be mixed is not uniformly dispersed and mixed within the plastic, resulting in the electromagnetic shielding filler being densely packed in the molded body, and electromagnetic waves leak from these sparse areas. Sometimes it happens. Furthermore, if the amount of the electromagnetic wave shielding filler mixed is increased in order to improve the shielding properties, there is a problem that the mechanical properties of the molded product, especially the impact resistance, deteriorate.

Means and Effects for Solving the Problems The present invention has been made in view of the above-mentioned problems, and is made by blow-molding a hollow molded product having a double-walled structure consisting of an outer wall and an inner wall. The hollow molded parts are molded into a shape that does not touch each other, and then the inside of this hollow molded product is filled with a paint that has radio wave shielding properties, and this paint is applied to the entire inside of the hollow part. I have to.

Example Embodiments of the present invention will be described based on the drawings.

Case 1 in the figure is a case of a personal computer to which the method of the present invention is applied.
The main body 2 and the lid 3 are joined at the mating surface PL, and both members are provided with electromagnetic wave shielding properties.

Hereinafter, a method of manufacturing one of the above-mentioned members, for example, the main body 2, will be explained with reference to FIG. 2 and subsequent figures.

A first mold 5 in which a concave cavity 4 having the outer shape of the main body 2 is molded and a second mold 7 in which a convex cavity 6 having the inner shape of the main body 2 is molded are placed between opposing sides. Then, after closing both the molds 5 and 7, the parison 8 is blow-molded by blowing air from the blowing device 8a, and the parison 8 is made up of an outer wall 2a and an inner wall 2b. Molding a hollow molded body with a heavy wall structure (3rd
figure). At this time, the inner facing surfaces of the outer wall 2a and the inner wall 2b are spaced apart over the entire surface.

Next, a paint 9 having electromagnetic wave shielding properties is filled into the hollow molded body using a paint filling device 10 (fourth
(Figure), apply the above paint to the periphery of the molded body. Thereafter, the excess paint inside the hollow body is discharged by the discharge device 11 and the hollow body is dried.

In the above process, a paint 9 having electromagnetic shielding properties is applied to the entire hollow inner surface of the main body 2, which is a hollow molded product, and radio wave shielding properties are imparted to the outer wall 2a and inner wall 2b of the main body 2.

In addition, the main body 2 is hollow, and if left as is, the inner and outer walls 2a and 2b may become unstable and cause bending, vibration, etc. Therefore, it is necessary to improve the strength and increase the storage volume. As shown in FIG. 5, both molds 5 and 7 may be further tightened to bring the outer wall 2a and the inner wall 2b into partial contact.

In the embodiment described above, the work of filling the paint 9 into the hollow molded body may be performed after the molded product is removed from the molds 5 and 7.

The parison 8 in the above embodiment is made of blow moldable plastic such as polyethylene, polypropylene, polyamide, ABS, etc.

Further, the electromagnetic shielding paint is made by mixing a binder such as acrylic or polyurethane resin with an electromagnetic shielding filler such as powdered silver, nickel, copper, or graphite.

The molding material and paint are not limited to those mentioned above, and any conventionally used materials may be used.

Effects of the Invention According to the present invention, it is possible to solve all the problems caused by the conventional means of obtaining radio wave shielding properties by using a mixed molding material containing a radio wave shielding exterior coating and an electromagnetic wave shielding filler. .

That is, it is possible to maintain a sanitary working environment, and even if the paint peels off, it will not adversely affect the items stored in the case. Further, since the paint is applied to the entire inner surface of the hollow body, the coating layer becomes double when viewed in the thickness direction of the container, and the electromagnetic wave shielding effect can be sufficiently achieved. Furthermore, the strength of the molded product is not affected by the radio wave shielding material, and it can be manufactured and handled in the same manner as ordinary hollow molded products.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a case to which the present invention is applied, and FIGS. 2 to 5 are process explanatory diagrams showing embodiments of the present invention. 2a is the outer wall, 2b is the inner wall, 5 and 7 are the molds, 8 is the parison, and 9 is the paint.

Claims (1)

[Claims] 1 Place the plasticized and melted parison 8 between the opposing split molds 5 and 7, and then
is closed and blow molded to create a hollow molded product with a double wall structure consisting of an outer wall 2a and an inner wall 2b.
The inner surfaces of the outer wall 2a and inner wall 2b are molded into a shape such that they do not touch each other, and then the inside of this hollow molded product is filled with a paint 9 having radio wave shielding properties, and the paint 9 is applied to the entire hollow surface. A method for producing an electromagnetic shielding molded article, characterized in that the paint is then discharged and then dried.