JPS6218799A - Electromagnetic wave 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 [Industrial Field of Application] The present invention relates to an electromagnetic shielding material, particularly in the form of a nonwoven fabric.

[Conventional technology]

In order to prevent the electromagnetic waves generated from electronic devices from having an adverse effect on the circuits of other electronic devices, it is necessary to cover the electronic devices with an electromagnetic wave shielding material. In many cases, the inside of the device's case is lined with metal sheets or coated with conductive paint, which acts as a shielding material. However, the housing has openings for ventilation, and electromagnetic waves leak through there. Furthermore, leakage of electromagnetic waves also occurs from the parts where the housing members are joined. Particularly at joints forming corners, the shielding material is bent along the corners, which tends to tear and cause leakage.

Conventionally, research has been conducted on electromagnetic shielding materials that can shield while maintaining ventilation in openings and are flexible enough to adapt to corners. Electromagnetic shielding materials based on non-woven fabrics have also been studied; for example, Japanese Utility Model Application Publication No. 16789/1989 discloses a non-woven fabric mixed with metal oxide powder. In addition, there are also non-woven fabrics made of synthetic fibers plated with electroless metal and used as electromagnetic shielding materials. However, many of these electromagnetic shielding materials have insufficient conductivity and have low shielding performance against electromagnetic waves, others have good shielding performance but are expensive and are difficult to put into practical use. There are also materials available, but the breathability of the non-woven fabric is compromised, and the paint tends to tear at the bends along the corners.

[Problem that the invention seeks to solve]

As described above, a breathable and flexible electromagnetic shielding material with sufficient performance has not yet been obtained.9 The present invention solves these problems and provides a material with good breathability and flexibility. However, the aim is to provide an electromagnetic shielding material with excellent shielding performance.

[Means for solving problems]

The electromagnetic shielding material of the present invention for solving the above problems is a nonwoven fabric containing at least 40% by weight of metal fibers and having a fiber basis weight of at least 20 g/2.

[Effect]

Electrical and magnetic wave shielding materials are thought to absorb electromagnetic waves and reflect them to attenuate or block them due to their conductivity.
The nonwoven fabric constituting the electromagnetic shielding material of the present invention contains metal fibers in the above weight ratio, and since the fibers have the above basis weight, entanglement of the metal fibers can be obtained. In other words, the surface resistance is approximately 40Ω or less, sufficient conductivity is obtained, and the practically required electromagnetic wave attenuation ability is 2.
Exceeds 0dB. If the weight ratio of gold 1ijE fibers and the weave amount of m fibers are less than these, the conductivity will be insufficient and the attenuation of the FrL magnetic waves will also be insufficient.

Furthermore, since the electromagnetic shielding material of the present invention is a nonwoven fabric, it is breathable and flexible.

(Example) The manufacturing performance of the nonwoven fabric constituting the electromagnetic shielding material to which the present invention is applied is evaluated in the following Examples 1 to 6.The nonwoven fabric in each example was made by a dry method, and the metal tam was 8. Denier stainless steel fibers and polyester Fa male are used as binder fibers.Although Comparative Examples 1 and 2 use the same fibers as above, they are examples to which the present invention is not applicable. be.

Example 1. A random web consisting of 40 parts by weight of metal fibers and 60 parts by weight of binder fibers is thermally bonded to obtain a nonwoven fabric having a basis weight of 55 g/2.

Example 2 A random web consisting of 50 parts by weight of metal fibers and 50 parts by weight of binder fibers is thermally bonded to obtain a nonwoven fabric having a basis weight of 603/a2.

Example 3 A random web consisting of 50 parts by weight of metal fibers and 50 parts by weight of binder fata is processed by needle punching to obtain a nonwoven fabric having a basis weight of /m0 g/+2.

Example 4 A random web consisting of 50 parts by weight of metal fibers and 50 parts by weight of binder fibers is thermally bonded while being embossed to obtain a nonwoven fabric having a basis weight of /m0 g/m2.

Example 5. 88 parts by weight of a random web made only of metal fibers was impregnated with 2 parts by weight of binder resin and thermally bonded to obtain a nonwoven fabric having a basis weight of 200 g/m2.

Example 6 A random web consisting of 50 parts by weight of metal ays and 50 parts by weight of binder fibers is thermally bonded to obtain a nonwoven fabric having a basis weight of 20 g/m2.

The reason why the basis weight is reduced at the same weight ratio compared to Example 1 is that a thinner am was used as the binder ma to increase the bulk.

Comparative example 1. A random web consisting of 50 parts by weight of metal fibers and 50 parts by weight of binder fibers is thermally bonded to obtain a nonwoven fabric having a basis weight of 15 g/m2.

Comparative Example 2. A random web consisting of 35 parts by weight of metal fibers and 65 parts by weight of binder fibers is thermally bonded to obtain a nonwoven fabric having a basis weight of 40 gets2.

The performance of each example and comparative example is shown in the table below.

The nonwoven fabrics of each example, which are surface electromagnetic wave shielding materials, all have sufficient air permeability and flexibility.

Note that although a random web was used as the nonwoven fabric in each of the above-mentioned Examples, equivalent results were obtained even when a carded web was used. The thickness of the metal fiber can range from about 3 to 13 denier. In addition to stainless steel fibers, any metal fibers or alloy fibers such as steel fibers, brass fibers, aluminum fibers, steel fibers, and silver fibers can be used as the metal fibers. In addition to polyester fibers, m-fibers such as polypropylene, acrylic, nylon, and polyethylene can be used as binder fibers.

In processing the nonwoven fabric, examples include embossing, needle punching, or simply heat-sealing. Among these examples, the embossed material has the lowest surface resistance, and the zero-order material has the highest electromagnetic wave shielding performance and is needle punched. This is because the degree of adhesion at intervals of m is higher in this order.

〔Effect of the invention〕

As explained above, the nonwoven fabric that is the electromagnetic wave shielding material to which the present invention is applied has a surface resistance of approximately 40Ω or less, sufficient conductivity, and the practically required electromagnetic wave attenuation ability exceeds 20 dB. Become. Since it is breathable and flexible, it can shield the opening of an electronic device's housing while maintaining ventilation, and can also be bent to accommodate corners. Moreover, since it is a non-woven fabric, it is easier to manufacture and cheaper than woven fabric.

Claims (1)

[Claims] 1. An electromagnetic shielding material comprising a nonwoven fabric containing at least 40% by weight of metal fibers and having a fiber basis weight of at least 20 g/m^2.