JPS58212199A - Electromagnetically shielding material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electromagnetic shielding material used for housings of electronic devices and the like.

Since electronic devices generate high frequencies that adversely affect peripheral devices such as televisions and radios, such as noise, it is necessary to shield such interfering radio waves, that is, to provide electromagnetic shielding.

In particular, synthetic resin housings are often used in recent electronic devices, and since this material transmits the above-mentioned interference radio waves, various methods have been adopted to electromagnetically shield them.

Examples include zinc spraying, coating with conductive paint such as silver, copper, or nickel, vacuum deposition, or mixing of conductive filler.

Zinc thermal spraying has an excellent shielding effect, but has the disadvantages of high cost, requiring surface treatment as a pretreatment, poor mass production, and poor working environment.

Although conductive paints have the advantage of being easy to apply using simple equipment, they currently have problems such as durability, cost, and productivity.

Additionally, vacuum evaporation requires a base coat to improve adhesion to the synthetic resin, and a coating layer to protect the surface, and because it involves batch processing, productivity may be poor. The cost is high and it is difficult to obtain a uniform deposited film.

On the other hand, unlike the surface treatment methods mentioned above, the method of mixing conductive filler has the advantage of not having to worry about peeling, corrosion, or occurrence of cranks, and can be produced using existing processes. It has the advantage of being able to be assembled immediately. However, in order to obtain a sufficient shielding effect, it is necessary to mix a large amount of filler, and if a large amount of filler is added, the problem arises that the physical properties of the synthetic resin will be impaired.

An object of the present invention is to obtain an electromagnetic shielding material having a sufficient electromagnetic shielding effect without impairing the basic physical properties of the resin by mixing flakes into a synthetic resin.

Hereinafter, the present invention will be explained based on the accompanying drawings.

FIGS. 1 and 2 show the structure of the conductive flake used in this invention. 1. The thin piece 1 is made by providing metal layers 3 of the same type or different types on both sides of a synthetic resin base material 2, and is manufactured by, for example, laminating a metal foil onto a synthetic resin film and then cutting it into thin pieces. do. Alternatively, the synthetic resin base material 2 may be formed into thin pieces after metal vapor deposition on both sides thereof.

The above metals include aluminum, copper, tin, nickel,
You can choose from lead, gold, silver, etc.

When using foil, aluminum is most preferable from the viewpoint of cost and placement, and a thickness of about 5 to 10 μm is appropriate from the viewpoint of conductivity, durability, etc.

Note that in order to prevent oxidation of the metal layer 3 and reduce contact resistance, another metal vapor deposition film 3' may be provided as shown in FIG.

Next, as the resin used for the base material 2, it is preferable to select a resin that can be formed into a film. Examples include polyimide, polystyrene, acrylic, vinyl chloride, styrene, nylon, polypropylene, and polyethylene.

The shape of the thin piece 1 formed using the above material is as follows:
Various choices are possible, but rectangular shapes, ie, squares and rectangles, are common. In addition, considering the need for uniform dispersion and ease of molding when mixed into a synthetic resin, which will be described later, the thickness of the thin piece 1 is 20 to 150 mm. μ, medium 0.1 to 3 am, and length 0.1 to 4 am or so.

As is clear from FIG. 3, the end and side surfaces of the thin piece 1 are not covered with the metal layer, and the end and side surfaces of the base material 2 are exposed.

The electromagnetic shielding material of the present invention can be obtained by mixing the thin piece 1 described above as a filler into a synthetic resin 4 as shown in FIG. The synthetic resin 4 can be arbitrarily selected as long as it can be injection molded, and examples thereof include polyimide, polystil, acrylic, vinyl chloride, styrene, nylon, polypropylene, and polyethylene.

As mentioned above, the base material 2 is exposed on the end and side surfaces of the thin piece 1, so if it is mixed into the synthetic resin 4 as described above, it will have excellent adhesion and may impair the mechanical properties of the shielding material. It is preferable to select the same resin as the base material 2 in order to improve adhesion.

Furthermore, in order to improve the physical properties of the electromagnetic shielding material, it is preferable to mix as little flake 1 as possible. However, there is a problem in that sufficient shielding performance cannot be obtained.

Here, since the shielding property of conductive fillers generally depends on the connection between individual fillers, that is, the quality of continuity, even if the number of thin pieces 1 is as small as possible, as shown in FIG.
If they can be mixed so that they are in contact with each other, it is possible to improve the shielding properties. To this end, it is preferable to mix in a material that has a bending strength higher than a certain level of the synthetic resin that will become the base material 2 of the thin piece 1.

Materials that wrinkle or bend during kneading or molding not only impair the physical properties of the synthetic resin and make it brittle, but also reduce the chances of contact with other flakes; If it has a hardness, it will be difficult to bend.

and helps maintain connectivity with other flakes.

Note that it is not necessary to mix only thin pieces of the base material with high bending strength, and even if a thin piece with high bending strength is mixed into a normal base material, the connectivity can naturally be improved.

The mixing ratio of flake 1 to synthetic resin 4 is 10 to 80% by weight, or more than 10% of it is 500χ10-6
Guin/Ca's songs are preferably thin pieces with strength.

Furthermore, in order to enhance the electromagnetic shielding effect, it is a good idea to mix various flakes with different sizes.

The electromagnetic shielding material obtained in the above manner has a volume resistivity of 10-3 to 10Ω, and has a sufficient electromagnetic shielding effect, but if it also has a magnetic shielding effect at the same time, the product value will further increase. do.

Therefore, it is possible to achieve the objective by kneading metal powder with high magnetic permeability into the resin that becomes the base material 2 in advance.This metal powder includes iron powder, ferrite powder, etc. It is necessary to mix 50% by weight or more. However, if it exceeds 80%, it becomes difficult to form the resin into a film.

According to the present invention, as described above, by mixing conductive thin pieces with high bending strength into 1, a sufficient electromagnetic shielding effect can be obtained without impairing the physical properties of the resin serving as the shielding material, and furthermore, the thin pieces Since the base resin is exposed on the end and side surfaces, it has excellent adhesion to the resin of the shielding material, and in this respect as well, a shielding material with good physical properties can be obtained.

Additionally, since it uses a thin piece of resin film with a thin metal layer, it is lighter than silver, copper, carbon fiber, aluminum flakes, etc.

In addition, by mixing iron powder or the like into the base material of the flakes, there is an advantage that a magnetic shielding effect can be achieved at the same time.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views showing the structure of a thin piece used in the shielding material of the present invention, and FIG. 3 is a perspective view of the same thin piece as above.
FIG. 4 is a sectional view showing the shielding material of the present invention. DESCRIPTION OF SYMBOLS 1... Conductive thin piece, 2... Base material, 3... Metal layer,
3'...Metal vapor deposition j conversion, 4...Synthetic resin'11

Claims (1)

[Claims] +11 An electromagnetic shielding material comprising a synthetic resin base material and a conductive thin piece having metal layers on both sides mixed in a synthetic resin at a ratio of 10 to 80% by weight. (2) The electromagnetic shielding material according to claim 1, wherein 50 to 80% by weight of metal powder with high magnetic permeability is mixed into the synthetic resin base material. (31+iiJ thin piece has a thickness of 20 to 150μ, r1] of 0.1 to 3 mm, and a length of 0.1 to 4
The electromagnetic shielding material according to claim 1, which is mm. (4) The electromagnetic shielding material according to claim 1, wherein the synthetic resin base material and the resin in which the flakes are mixed are the same type of synthetic resin.