JPH0745989A - Electromagnetic-wave shield material - Google Patents

Abstract

PURPOSE:To correspond to a requirement at a high degree regarding electromagnetic-wave shield properties by laminating a surface layer material on both surfaces or one surface of an electromagnetic-wave shield layer consisting of a metallic-fiber nonwoven fabric and a thermo-setting resin. CONSTITUTION:It is favorable that a metallic fiber having a mean fibrous diameter of 50mum or less and mean fibrous length of 5-100mm is used as a metallic fiber constituting a metallic-fiber nonwoven fabric, and one kind or more of metals selected from a ground composed of Fe, Al, Ni and Cu are employed. The metallic-fiber nonwoven fabric constituting an electromagnetic- wave shield layer is set in 50wt.%, or less of a shield layer, and a phenol resin, an epoxy resin, an unsaturated polyester resin, etc., are used as a thermo-setting resin configuring the electromagnetic-wave shielding layer. Accordingly, the electromagnetic-wave shield material is constituted by using plastics, wood, leather, cloth, a rubber, paper, a coating film, etc., as a surface layer material, and the electromagnetic-wave shield material having excellent electromagnetic- wave shield properties and being at no issue in moldability and workability is acquired.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic wave shielding material which is excellent in electromagnetic wave shielding property and has no problem in moldability and workability.

[0002]

2. Description of the Related Art Due to the trend toward lighter weight and smaller size, plastic molded products have been widely used as a substitute for metal, but with the spread of personal computers and word processors, there are new problems such as electrostatic damage and electromagnetic interference. It is an indispensable prerequisite for the development of OA equipment to give rise to problems and to provide OA equipment with excellent electromagnetic wave shielding properties. Further, due to the development of electronic technology, electromagnetic wave shielding properties are required in all fields other than OA equipment.

The following techniques are known as a method for imparting an electromagnetic wave shielding property to a plastic molded product. A technology for forming conductive coatings on plastic molded products by methods such as plating, vapor deposition, metal spraying, sputtering, and coating with conductive paint. As disclosed in JP-A-62-122300, FRP
A technology to attach a conductive material made of carbon fiber non-woven fabric as the inner layer of a molded product. As disclosed in Japanese Examined Patent Publication No. 56-51186, in the polycarbonate resin molded product, aluminum alloy coated glass fiber, or metal filler, metal fiber, carbon beads,
Technology for mixing conductive materials such as carbon fiber.

[0004]

However, the above-mentioned prior art has the following problems. In the technique of forming a conductive coating of, it is difficult to form a conductive coating of uniform thickness on the surface of a plastic molded product having a complicated shape with bosses, ribs, etc.
In addition, there is a problem in that the conductive substance drops off from the surface of the plastic molded product, causing a short circuit in the internal circuit and troublesome secondary processing. In the technique of attaching the conductive material of, it is difficult to accurately attach the conductive material to the surface of the FRP molded product having a complicated shape with bosses, ribs, etc., and it is difficult to reduce the thickness of the secondary material. Since the processing is complicated, there is a problem that mass productivity is low. In the technique for mixing conductive material, the secondary processing is not troublesome, but there are the following problems depending on the conductive material used.

That is, -1: When a metal filler or a metal fiber is used as the conductive material, there are problems that the specific gravity of the molded product remarkably increases and the moldability is impaired. -2: When using carbon beads, it is necessary to mix a large amount of them in order to obtain sufficient electromagnetic wave shielding properties, and as a result, the basic physical properties of the plastic molded product, such as toughness, are impaired. I have a problem. -3: When metal-coated glass fibers are used, the cost is high because the fibers themselves are expensive, and the thin metal coating on the fiber surface is easily deteriorated by heat shock, oxidation, etc., and the reliability of the electromagnetic wave shielding property is high. There is a problem of lacking. -4: When carbon fibers are used, carbon fibers having a short fiber length, that is, carbon fibers having a fiber length of less than 10 mm are used from the viewpoint of avoiding troubles during molding, and therefore sufficient electromagnetic wave shielding properties are obtained. In order to obtain it, it is necessary to increase the plate thickness of the molded product or increase the carbon fiber content, so the amount of carbon fiber used will increase, the fluidity of the molding material will be significantly impaired, and the cost will increase. There is a problem. In addition to the above, when the carbon fiber is used in the form of woven fabric, there is a problem that it is difficult to form a molded product having a structure having a large number of bosses, ribs and the like inside.

Under such circumstances, recent electronic devices have been further developed remarkably, and a higher level of electromagnetic wave shielding property has been required.
Then, the present inventors succeeded in providing a molding material for an electromagnetic wave shield which can meet a high demand for the electromagnetic wave shielding property by conducting various studies and solving the above problems.

[0007]

The electromagnetic wave shielding material of the present invention uses a metal fiber non-woven fabric as a conductive material. A surface layer material is laminated on both sides or one side so as to be the front surface or the back surface of the molded product.

[0008]

The metal fibers constituting the metal fiber nonwoven fabric used in the present invention have an average fiber diameter of 50 μm or less and an average fiber length of 5 to 5.
It is preferable to use a metal having a diameter of 100 mm, and it is recommended to use at least one metal selected from the group consisting of Fe, Al, Ni, and Cu as the metal. The amount of the metal fiber nonwoven fabric constituting the electromagnetic wave shield layer is 50% by weight or less of the shield layer, but preferably 10% by weight or more is recommended. Phenolic resins, epoxy resins, unsaturated polyester resins, and the like are used as the thermosetting resin forming the electromagnetic wave shield layer, and these may be blended or alloyed.
Further, as the surface layer material in the present invention, plastic,
Wood, leather, cloth, rubber, paper (including pulp aggregate), coating film and the like are used.

As the metal fibers, the average fiber diameter is 10 μm or less,
Further, the reason why the average fiber length of 5 to 100 mm is recommended is that it is suitable for improving moldability, surface property and mechanical strength. That is, when the average fiber diameter exceeds 10 μm, when the surface layer material is thin, metal fibers may be exposed on the surface of the molded product. Further, if the average fiber length exceeds 100 mm, the entanglement of the fibers becomes complicated, and lumps of the fibers are liable to be formed, which may deteriorate the moldability and surface property. The average fiber length is preferably 5 mm or more, and if it is less than 5 mm, both the electromagnetic wave shielding property and the mechanical strength are extremely reduced.

Fe, Ni, C as the metal of the metal fiber
One or more metals selected from the group consisting of r, Al, and Cu or alloys containing them are mainly used, and if necessary, other metals can be used in a slight amount. In producing the electromagnetic wave shield material of the present invention, a prepreg is prepared by impregnating a metal fiber nonwoven fabric with a thermosetting resin, and pressing the prepreg in a state where a surface layer material is placed on both sides or one side of the prepreg. Good.

[0011]

Example 1 Metal fiber (Fe, average fiber diameter: 5 μm, average fiber length: 5
0 mm) non-woven fabric with thermosetting resin (phenolic resin)
(Amount of metal fiber: 40% by weight), and both sides of the sheet-shaped product made into prepreg are sandwiched by sheet-shaped prepreg made of carbon fiber nonwoven fabric impregnated with thermosetting resin,
When the obtained molding material having a sandwich structure was hot-pressed, an electromagnetic wave shielding material having excellent surface properties and processability was obtained. The electromagnetic wave characteristics and Izod impact value are as shown in Table 1.

Example 2 Metal fiber (Fe, average fiber diameter: 5 μm, average fiber length: 5
0 mm) non-woven fabric with thermosetting resin (phenolic resin)
Is impregnated with (metal fiber amount: 30% by weight), and the surface of a sheet-like material obtained by prepregizing this is covered with a wooden sheet using a thermosetting resin as an adhesive, and the back surface is covered with a glass fiber nonwoven fabric, It was formed by hot pressing.

Comparative Example CFRP was molded and processed only with a sheet-like prepreg obtained by impregnating a carbon fiber nonwoven fabric with a thermosetting resin (phenolic resin). The electromagnetic wave characteristics and the Izod impact value are also shown in Table 1 for comparison.

[0014]

[Table 1]

The electromagnetic wave shielding material is, as shown in Table 1,
Compared to the CFRP of the comparative example, the magnetic shield property is improved, and the moldability and workability are comparable to those of the CFRP of the comparative example, and not only simple plate-shaped molded products but also molded products with complicated shapes. It can be easily manufactured. Further, since the metal fiber is added, C of Comparative Example
The impact value was twice as high as that of FRP.

[0016]

EFFECTS OF THE INVENTION Since the present invention is constructed as described above, it is possible to provide an electromagnetic wave shielding material which has a good electromagnetic wave shielding property and has no problem in moldability and workability.

Claims (4)

[Claims] 1. An electromagnetic wave shielding material comprising a surface layer material laminated on both surfaces or one surface of an electromagnetic wave shielding layer made of a metal fiber nonwoven fabric and a thermosetting resin. 2. The metal fibers constituting the non-woven metal fiber nonwoven fabric have an average fiber diameter of 50 μm or less and an average fiber length of 5 to 10.
The electromagnetic wave shielding material according to claim 1, which has a thickness of 0 mm. 3. A metal fiber mainly composed of at least one metal selected from the group consisting of Fe, Ni, Cr, Al and Cu, or an alloy containing them, as the metal fiber constituting the metal fiber nonwoven fabric. The electromagnetic wave shielding material according to claim 1 or 2, which is used. 4. The electromagnetic wave shield material according to claim 1, wherein the electromagnetic wave shield layer contains 50% by weight or less of a metal fiber nonwoven fabric.