JPH0758490A - Electromagnetic shielding material - Google Patents

Abstract

PURPOSE:To provide electromagnetic shielding material which can improve electromagnetic shielding property without deteriorating original physical properties of resin base material. CONSTITUTION:A sheet 1 for electromagnetic shielding is formed by unifomly mixing and dispersing ferrite ultrafine particles 5 in polyurethane rubber 3 being resin base material. The polyurethane rubber 3 is manufactured through processes such as well-known urethane reation and crosslinking reaction. The ferrite ultrafine particles 5 have a grain diameter of about 0.1-1mum and 20-60wt.% of the particles are mixed and dispersed in the polyurethane rubber 3. The ferrite ultrafine particles 5 are manufactured by, e.g. a spray drying method (a method wherein metal salt solution is sprayed and dried). The ferrite ultrafine paticles 5 are mixed in the polyurethane rubber 3, in an arbitrary manufacturing process before the polyurethane rubber 3 is turned into a sheet as the final form.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic wave shield material used for, for example, a container for electronic equipment.

[0002]

2. Description of the Related Art Conventionally, as an electromagnetic wave shielding material that absorbs or reflects an electromagnetic wave from the outside, powder or fiber (conductive filler) made of a conductive material such as carbon black, metal or ferrite in a synthetic resin substrate. It is known to mix and disperse, and is used, for example, as a container for various electronic devices. This conventional electromagnetic wave shielding material is provided with an electromagnetic wave shielding property by mixing a conductive filler such as carbon black to reduce the electric resistivity of the synthetic resin.

[0003]

However, in the above-mentioned conventional electromagnetic wave shielding material, when an attempt is made to improve the electromagnetic wave shielding effect by increasing the mixing amount of the conductive filler such as carbon black, the physical properties of the resin base material are reduced. The problem of deterioration arises. That is, due to an increase in the amount of conductive filler mixed, mechanical strength such as bending strength and tensile strength decreases, or elasticity (that is, resilience to tension and compression) when the resin base material is rubber (elastomer). Occurs.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an electromagnetic wave shielding material capable of improving the electromagnetic wave shielding property without deteriorating the original physical properties of the resin base material.

[0005]

Means for Solving the Problems The present invention for achieving the above-mentioned object is summarized as an electromagnetic wave shielding material characterized in that ultrafine particles having an electromagnetic wave shielding effect are dispersed in a resin base material. .

The type of the resin base material is not particularly limited, and examples thereof include hydrocarbon resins (polyethylene, polypropylene, polystyrene, etc.), halogen-containing resins (polyvinyl chloride, polyvinylidene chloride, etc.), acryl. -Based resin, vinyl acetate-based resin, polyester-based resin, polyamide-based resin, polyether-based resin, phenol-based resin, amino-based resin, urethane-based resin, epoxy-based resin,
Known synthetic resins such as silicone resins can be used. Further, a natural resin can be used as the resin base material.
It should be noted that these resin base materials may be colored in a desired color as necessary, or additives such as a plasticizer, a deterioration inhibitor, and a light stabilizer may be added.

The above-mentioned ultrafine particles generally have a particle size of about 1
The particle size is less than or equal to μm and has a unique property not found in bulk or large particles because the particle size is very small (for example, functional material, June 1993 issue, Vol. 1).
3, No. 6). In the present invention, particles having a particle size of 1 μm or less are used, more preferably the particle size is 0.1 μm.
The following are used:

The material of the ultrafine particles is not particularly limited as long as it has an electromagnetic wave shielding effect.
Examples thereof include metals such as 1, Fe, Co, Ni and Cu, ferrite, carbon black, far infrared ceramics and the like. In addition, it is preferable to use ultrafine particles made of an amorphous metal, because a more excellent electromagnetic wave shielding effect is exhibited. Furthermore, ultrafine particles of different materials may be mixed and mixed, for example, carbon black and ferrite, or amorphous metal and ferrite may be mixed and mixed.

The ultrafine particles can be obtained by a known production method, and a production method in which they are physically produced in a gas phase, a production method by a chemical reaction in a liquid phase or a gas phase, and the like are used. Here, as a physical manufacturing method, for example,
In-gas evaporation method that evaporates and cools metal in an inert gas, sputtering method that utilizes sputtering phenomenon, metal vapor synthesis method that co-evaporates evaporated metal atoms on a substrate with a solvent, fluid oil that evaporates metal on oil Examples include upper vacuum evaporation method. Examples of the production method by a liquid phase chemical reaction include a colloid method using a surfactant, an alkoxide method utilizing hydrolysis of a metal alkoxide, a coprecipitation method, and a uniform precipitation method. Further, as a production method by a chemical reaction in a gas phase, for example, a thermal decomposition method of an organometallic compound (such as a metal carbonyl compound), a method of reducing or oxidizing a metal chloride in a reaction gas stream, an oxide or a hydrate ( For example, a method of reducing (α-FeOOH) in hydrogen, a solvent evaporation method of spraying and drying a metal salt solution, etc. can be mentioned.

The electromagnetic wave shielding material of the present invention is obtained by mixing the above-mentioned ultrafine particles into a resin base material, and molding the resin base material into a desired shape by a known molding method according to the application. Can be used. Here, the amount of the ultrafine particles mixed into the resin base material is too large, the characteristics of the resin base material are impaired, and conversely, if the amount is too small, a sufficient shielding effect cannot be exerted. You can increase or decrease. As the molding method, for example, compression molding, transfer molding, injection molding, cast molding, extrusion molding,
Examples include calendar molding and blow molding.

Since the electromagnetic wave shielding material produced in this manner is mixed with ultrafine particles having an extremely small particle diameter, the original physical properties of the resin base material are not impaired. That is, mechanical strength such as tensile strength, compressive strength, and bending strength does not decrease, or elasticity does not decrease when the resin base material is rubber.

The electromagnetic wave shielding material as described above can be suitably used, for example, as a storage container (housing) for various electronic devices, a sheet or a gasket for electromagnetic wave shielding. If a transparent resin such as an acrylic resin is used as the resin base material, it can be used as a window material.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of the electromagnetic wave shielding material of the present invention described above will be described with reference to the drawings. First, the first embodiment will be described. FIG. 1 shows an electromagnetic wave shield sheet 1 of the first embodiment. This sheet 1 is obtained by uniformly mixing and dispersing ferrite ultrafine particles 5 in polyurethane rubber 3 which is a resin base material.

Here, the polyurethane rubber 3 is manufactured through known steps such as urethanization reaction and crosslinking reaction. Further, the ferrite ultrafine particles 5 have a particle size of about 0.
It is about 1 to 1 μm and is mixed / dispersed in the polyurethane rubber 3 at a weight ratio of 20 to 60% by weight. The ultrafine ferrite particles 5 are manufactured by, for example, a spray drying method (a method of atomizing a solution of a metal salt in a solution and drying the metal salt). The mixing of the ferrite ultrafine particles 5 with the polyurethane rubber 3 is performed in any manufacturing process before the polyurethane rubber 5 is formed into a sheet shape which is the final shape.

According to the sheet 1 of such an embodiment, since the ultrafine ferrite particles 5 having an extremely small particle size are dispersed, good electromagnetic wave shielding properties are exhibited and, at the same time, the polyurethane rubber which is a resin base material is exhibited. There is an effect that the original elasticity of 3 (that is, the resilience to tension and compression) does not decrease significantly.

Next, a second embodiment will be described. Figure 2
FIG. 8 is a perspective view showing a housing 11 for electronic components according to a second embodiment. The housing 11 includes a case main body 13 and a lid 15 attached to the case main body 13 so as to be openable and closable. The case body 13 and the lid 15 are AB
S-resin 17 (acrylonitrile-butadiene-styrene copolymer) in which ferrite ultrafine particles 19 similar to those in the first embodiment are mixed and dispersed at a ratio of 20 to 60% by weight, and molded into a predetermined shape. Is.

Here, the case body 13 has a rectangular parallelepiped shape having an opening on the upper side, and a side face portion thereof is provided with a waterproof connector 21 for taking out signal lines (not shown) of electronic components to be housed to the outside. . In addition, the edge portion 1 of the case body 13
3a (that is, a portion where the case body 13 and the lid portion 15 are combined)
A substantially square-shaped electromagnetic wave shield gasket 19 is adhered to the base plate by a conductive adhesive. This electromagnetic wave shielding gasket 19 establishes electrical conduction between the case body 13 and the lid body 15 when the lid body 15 is closed, and the electromagnetic wave shielding sheet 1 of the first embodiment described above is used. It is shaped like a square bracket.

On the other hand, the lid 15 is attached to the hinge portion 23 of the case body 13 so as to be rotatable (that is, openable and closable). Further, the lid body fastening portion 15b is provided on the side portion 15a of the lid body 15 so that when the lid body 15 is closed, the case body 13 and the lid body 15 can be fastened by sandwiching the electromagnetic wave shielding gasket 19. Is provided.

According to the storage housing 11 of the second embodiment described in detail above, the case body 13 and the lid body 15 are made of the ABS resin 17 in which the ultrafine ferrite particles 19 having an extremely small particle size are mixed and dispersed. Since it is formed of a molded product, good electromagnetic wave shielding properties can be obtained and the ABS resin 17
There is an effect that the mechanical strength such as the compressive strength and the bending strength does not deteriorate and the electronic components housed inside can be sufficiently protected.

The embodiment of the present invention has been described above.
It is needless to say that the present invention is not limited to such embodiments and can be implemented in various modes without departing from the scope of the present invention. For example, the material of the ultrafine particles to be dispersed in the polyurethane rubber 1a or the ABS resin 17 is not limited to the ferrite, but Fe, C
It may be a metal such as o or carbon black.

Further, the kind of the resin base material is not limited to the above embodiment, and various kinds can be used according to the application. For example, when used as a window material for a building or the like, a transparent resin such as an acrylic resin can be used.

[0022]

As described in detail above, since the electromagnetic wave shielding material of the present invention is mixed with ultrafine particles having an extremely small particle size, the electromagnetic wave shielding property of the resin substrate is not deteriorated. It has a remarkable effect that it can be improved.

[Brief description of drawings]

FIG. 1 is a perspective view of an electromagnetic wave shielding sheet according to a first embodiment.

FIG. 2 is a perspective view of a housing for electronic components according to a second embodiment.

[Explanation of symbols]

1 ... Electromagnetic wave shielding sheet, 3 ... Polyurethane rubber, 5, 19 ... Ultra fine ferrite particles, 11 ...
・ Housing for electronic parts, 13 ・ ・ ・ Case body, 15 ・
..Lids, 17 ... ABS resin

Claims (1)

[Claims] 1. An electromagnetic wave shielding material comprising ultrafine particles having an electromagnetic wave shielding effect dispersed in a resin base material.