JPS6050902A - Electromagnetic wave absorbing sheet-form fibric material - Google Patents

Abstract

PURPOSE:To enable to obtain electromagnetic wave absorbing sheet material having flexibility, air permeability, light weight, and durability by a method wherein the surface of a conductive fibric material is coated with an electromagnetic wave absorbing material containing ferromagnetic powder and an organic polyer compound as the main constituents. CONSTITUTION:An electromagnetic wave absorbing layer 2 is formed by the coat of the surface of the conductive fibric material 3 with the electromagnetic wave absorbing material contaning ferromagnetic powder and an organic polymer compound as the main constituent to a desired thickness. In this case, according to the wavelength of electromagnetic waves to be absorbed, it is not always necessary to coat the entire surface with the absorbing material. The coat of the material 3 with said absorbing material in the form of lattice, mesh, perforation, and the like makes the great effect by the economization, reduction in weight, and increase in air permeability of the absorbing material. To obtain a thickness of over a fixed value, hardening a resin after an expanding agent is mixed in the composition of the aborbing layer and then expanded enables to obtain a thick electromagnetic wave absorbing layer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electromagnetic wave absorbing sheet-like fibrous material.

More specifically, an electromagnetic wave absorbing material mainly composed of ferromagnetic powder and an organic polymer compound is coated on the entire surface or partially of the S-electromagnetic fiber material to a desired thickness to absorb electromagnetic waves. This invention relates to an electromagnetic wave absorbing sheet-like fibrous material characterized by forming an absorbing N.

The amazing progress and widespread use of micro engineering 1 Noctro-X, which is based on digital technology, has deeply penetrated not only the industrial world, but also medical institutions and general households. Electromagnetic waves generated and emitted from the device itself can cause malfunctions that can lead to fatal situations.

As described above, electromagnetic waves as information media, especially high-frequency microwaves, are effectively used in various fields of daily life, but it is well known that electromagnetic interference can no longer be ignored and has become a social problem.

1.1 of the present invention is a means for eliminating electromagnetic interference as described above. To provide an electromagnetic wave-forming sheet-like fiber material that is lightweight and durable.

Electroless metal fiber materials have traditionally been used as conductive fibers or metallized fibers, but this material has a large electromagnetic wave transmission attenuation of 30 to 40 dB, and although it has a shielding effect, it is a thin metal film. Because of this structure, most of the electromagnetic waves are reflected, so the return loss is extremely small and it cannot be used as an electromagnetic wave absorbing material.

Such metallized fiber materials therefore have the disadvantage of causing disturbances due to reflected electromagnetic waves.

Furthermore, although carbon fiber materials with semiconductor properties can be used as absorbers due to dielectric loss of electromagnetic waves, the return loss of electromagnetic waves is only about 4 to 5 dB, which is still insufficient as an electromagnetic wave absorber II. It is not a thing, and its thickness cannot be made thinner.

The present invention is a novel fiber material that has not only an electromagnetic wave shielding effect but also an absorption performance, and is used as an electromagnetic wave absorbing layer that has both features.

The organic polymer compounds used in the present invention are mainly synthetic resins, such as polyester resin, pinylethyl acetate,
Noshi copolymer resin, RiooJJ+Noshimu acrylic resin,
Polyester resin, epoxy resin, urea resin, phenol resin, chloride heel resin end-polymerization or condensation product dissolved in an organic solvent u-G is an emulsion of 0//w or wlo 9 or an initial stage of these resins. Condensates etc. can be used.

In addition, the ferromagnetic material used in the present invention is ferrite (general formula: MFe2O4" M il divalent metal, such as Mn,
Ni.

It is a powder of Cu, Mlil, Zn, Cd, F'e Nato), iron, leek, cobalt, or an alloy of these metals, and the particle size is preferably in the range H of 1 to 500μ. be.

In order to obtain the largest amount of return attenuation at a target frequency, it is important to select the particle size of the ferromagnetic material, and it is well known that the frequency at which the return attenuation peaks differs depending on the particle size.

For example, if the particle size is in the range of 2 to 10μ, 1 Go, 5 to 10
The maximum value of return loss is between GHz and 50-500μ
For particles with a particle size of , the reflection attenuation becomes large between 0.6 and 2 GHz.

The amount of ferromagnetic powder added to the organic polymer compound resin liquid used in the present invention is most preferably 80 to 220 parts by weight per 100 parts by weight of the resin solid content, and if it is less than 80 parts, the electromagnetic wave absorption ability decreases. If the amount exceeds 220 parts by weight, the adhesiveness will decrease and the durability will decrease, which is not practical.

Various methods are available for applying these mixed compositions to the surface of the conductive fiber material, and by selecting an appropriate method, the desired thickness of the electromagnetic wave absorbing layer can be obtained. Moreover, mass production becomes possible.

In order to obtain the maximum return loss, it is necessary to adjust the thickness of the electromagnetic wave absorption layer according to the target frequency of absorbed electromagnetic waves.

To this end, it is possible to adjust the thickness of the electromagnetic wave absorbing layer by changing the coating method and coating amount of the absorbing layer composition.

However, it may be difficult to further increase the thickness with this alone.

In order to obtain a thickness above a certain level, a foaming agent is mixed into the absorbing layer composition and the resin is cured while foaming, thereby making it possible to obtain a thick electromagnetic wave absorbing layer.

Furthermore, it is possible to use a resin that foams itself, such as the resin used for threads.

The advantages of foaming the synthetic resin composition of the electromagnetic wave absorbing layer are not only the increased thickness of the absorbing layer, but also the increased flexibility and weight reduction compared to the same thickness. There is a big advantage.

Also, depending on the wavelength of the electromagnetic waves to be absorbed, it is not necessarily necessary to coat the entire surface with the absorbing material, but as shown in Figure 1, the sheet-shaped conductive fiber material (3) & absorbing material (2) may be coated in a checkered or mesh pattern. If applied with handles, holes, etc., the effects will be great, such as reducing the amount of electromagnetic wave absorbing material, reducing weight, and increasing breathability.

In addition, as shown in Fig. 2, since the sheet-like carbon fiber material (1) is an absorber of electromagnetic waves due to dielectric loss, the ferromagnetic electromagnetic wave absorbing layer coated on the surface of the conductive fiber material (3) It has been found that when (2) is added with dielectric loss, a synergistic effect can be obtained since dielectric loss is added to magnetic loss.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Fine ferrite powder 50 parts (weight) Synthetic resin liquid 50 parts Crosslinking agent 10 parts Catalyst 2 parts 4 The above compositions were mixed in a roll mill or a mill until homogeneous to obtain an appropriate viscosity. Prepare to obtain.

To coat the entire surface, the electromagnetic wave absorbing layer was coated on one side of the conductive fiber fabric using a knife coater, dried and coated twice, and the resulting electromagnetic wave absorbing layer had a thickness of 0.6 vyr+.

The results of measuring the electromagnetic wave reflection attenuation using an oscillator and a power meter showed the characteristics shown in Figure 3.

Example 2 Fine powder of ferrite 50 parts (weight) Acrylic acid ester 50 parts (:f7t) Crosslinking agent 4 parts Blowing agent (product name Nisanri Ropal etc.) 10 parts // The above composition was mixed with the above Example 1. In the same manner, it was applied to the surface of the sheet-like conductive fiber and dried. By varying the coating amount, foaming conditions, etc., we obtained film thicknesses of 1.0, 1.5, and 2.0 degrees, and measured the reflection attenuation in the same manner as above.
The results shown in the figure were obtained.

Example 3 The absorbent composition of Example 1 was applied to the surface of the conductive net Y to a thickness of 1.0 mm, and then a sheet 1-shaped carbon fiber material was laminated thereon.

After drying and heat treatment, the reflection attenuation F of electromagnetic waves was measured and the values shown in FIG. 5 were obtained.

[Brief explanation of the drawing]

The drawings show embodiments of the present invention, and are shown in FIGS.
C) is a front view thereof, FIG. 2 is a simplified sectional view showing another embodiment of the present invention, and FIGS. 3 to 5 are diagrams showing the relationship between electromagnetic wave reflection attenuation and frequency. (1)... Sheet-like carbon fiber material, (2)... Electromagnetic wave absorbing layer (3)... Conductive fiber material. Patent applicant: Takase Dye Factory Co., Ltd. Agent: Fusa Nakao, patent attorney

Claims (1)

[Claims] ■ An electromagnetic wave absorbing material mainly composed of ferromagnetic powder and an organic polymer compound is coated on the surface of a conductive fiber material to a desired thickness on the entire surface or in part to absorb electromagnetic waves. An electromagnetic wave absorbing sheet-like fiber material characterized by forming layers. (2) The electromagnetic wave absorbing sheet fiber according to claim 1, characterized in that the electromagnetic wave absorbing layer is foamed to a desired thickness by mixing a foaming agent or a foamable synthetic resin in the electromagnetic wave absorbing material. Wholesale, materials. ■ Claim 1, characterized in that sheet-like carbon fibers are laminated with an electromagnetic wave absorbing layer in the middle.
The electromagnetic wave absorbing sheet-like fiber material described in 2.