JPS6323397A - Electromagnetic shielding material - Google Patents

Abstract

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

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is an electromagnetic shield that absorbs electromagnetic waves by reflecting a part of the irradiated electromagnetic waves and converting the remaining electromagnetic waves that are not reflected into thermal energy. It is related to materials.

(Prior art) With the recent spread of various office automation equipment, the electromagnetic waves that are harmful to the human body, emitted from their separate devices by 6 inches in width, have become a problem, and there is a need for a means to protect humans from electromagnetic waves. .

In addition, for testing and evaluation of electronic equipment such as electronic communication equipment, a shielded clean room is required to prevent unnecessary electromagnetic waves from flying into the room.

Conventionally used electromagnetic shielding materials include those in which a fiber base material is plated with metals such as gold, silver, nickel, and copper. In addition, there are also those in which a metal tube is printed on a fiber base material, and those in which metal wires such as copper wire are woven into fabric.

(Problem to be solved by the invention) However, the conventional electromagnetic shielding material described above simply reflects electromagnetic waves by a metal layer with high electrical conductivity on its surface, and absorbs electromagnetic waves and generates heat energy. It was not something that would be destroyed by converting it into something. Therefore, although conventional electromagnetic shielding can be used as clothing to protect the human body from electromagnetic energy, it can be used on the wall of a shield clean room or attached to a separate device to prevent the electricity radiated from it. We could not expect any effect from absorbing corporate waves.

(Means for Solving the Problems) The purpose of the present invention, as a result of intensive research and consideration in view of the drawbacks of the above-mentioned conventional techniques, is to , reflects electromagnetic waves,
Another object of the present invention is to provide an electromagnetic shielding material that has the property of converting unreflected electromagnetic waves into thermal energy.

That is, the present invention relates to an electromagnetic shielding material characterized in that it is formed by directly or indirectly layering a synthetic resin layer containing graphite powder on a fiber base material.

The fibers and base materials used in the present invention are not particularly limited, and include, for example, natural fibers such as cotton, wool, and silk, rayon,
Regenerated fibers such as acetate, polyester, polyamide,
Woven and knitted fabrics made of synthetic fibers such as aromatic polyamide,
Any non-woven fabric etc. can be used. Further, these fiber base materials can also be used after being dyed or subjected to water repellent treatment.

In the present invention, metal plating may be applied to one or both surfaces of the fiber base material in advance for the purpose of further improving shielding properties.

The graphite powder having electromagnetic wave shielding properties used in the present invention will be explained below.

In general, the crystal structure of graphite is such that carbon atoms are arranged in a regular hexagon as shown in FIG. 2, and each carbon atom is bonded to three other carbon atoms through covalent bonds. Roughly speaking, as shown in Figure 2, they are connected in a number of planes and strongly connected, and each plane constitutes a layered structure. The layers of these layered structures are bonded together by van der Waals forces, but this bonding force is weak and easily sheared when subjected to shearing force. Graphite has excellent thermal conductivity, and also has excellent characteristics of changing thermal energy with respect to electrical resistance, which allows it to absorb electromagnetic waves.

Among graphites, what is called quiche graphite, which is precipitated in flakes on the surface of cast iron due to supersaturation of carbon contained in molten iron during cast iron production, has a lattice constant of C=6.
708, specific gravity: about 2.20, and has an extremely high degree of graphitization, almost matching the perfectly crystalline C-6,7079 of graphite, specific gravity: about 2.266 (theoretical value). There is.

Further, since Quiche graphite has a large aspect ratio as an attribute of being precipitated in a solution, it can absorb electromagnetic waves in a wide frequency range.

The present invention uses such graphite, particularly preferably the above-mentioned Quiche graphite, with a particle size of 5 to 100 μm, more preferably 10 to 40 μm.
It is characterized in that it is mixed into a synthetic resin and provided directly or indirectly on the fiber base material in one or more layers.

In the present invention, specific examples of synthetic resins containing graphite powder include polyurethane, polyacrylic ester, polymethacrylic ester, polyamide, polyester,
Examples include 8S resin, polyvinyl chloride, polyolefin, polysulfone, ethylene-vinyl acetate copolymer, polyvinylidene chloride, epoxy resin, fluororesin, styrene resin, acrylic resin, and the like.

The content of electromagnetic shielding graphite powder in the synthetic resin is particularly limited if it is necessary to ensure that the electromagnetic shielding material as a final product reflects a part of the electromagnetic waves and converts the electromagnetic waves into thermal energy. There are no restrictions, and the law can be determined as appropriate depending on the desired performance and purpose of use. However, for normal purposes, the amount is about 7 to 120 parts by weight, preferably 50 to 1 part by weight.
00 parts by weight of graphite powder is required. In this case, if 7
If the amount is less than 1 part by weight, the electromagnetic shielding effect will be poor, and
If it exceeds 20 parts by weight, the reflectance will be high and the electromagnetic wave absorption effect will be weakened.

Metal powder, metal oxide, etc. may be appropriately added to the graphite powder used in the present invention for the purpose of adjusting reflectance and the like.

As a practical embodiment of the electromagnetic shielding material according to the present invention, the following three types of synthetic resin layers containing graphite can be laminated on a fiber base material in combination depending on the purpose of use.

△, stabilizer, cross) n agent, etc., electromagnetic shielding synthetic resin layer B for adhesion purposes, electromagnetic shielding synthetic antigrease layer C9 that contains the largest amount of graphite and has a large electromagnetic shielding effect; Electromagnetic shielding synthetic resin layer for the purpose of protection such as flexibility and flexibility The electromagnetic shielding material according to the present invention can be obtained by appropriately selecting and combining the above three layers in consideration of their special characteristics. preferable. In particular, in consideration of durability, it is preferable to use a layer in which layer B, which has high electromagnetic shielding properties, is directly or indirectly laminated on the fiber base material by layer A and layer 0.

Examples of the relationship with the fiber base material include the following.

(1) Fiber base material/A/B/C (2) Fiber base material/B/C (3) Fiber base material/A/C (4) A/Fiber base material/A/B/C (5) C/Fiber base material/A/B/C FIG. 1 shows a sectional view of the embodiment (1) above.

In addition, in (4) and (5) above, a plurality of A layers, C
@ may be composed of the same composition or may be composed of different compositions.

In addition, although the above example shows the case where each of the layers A, B, and C contains graphite, the present invention also includes the case where the A layer or the 0 layer does not contain graphite.

The thickness of each layer varies depending on the purpose of use, but the thickness of layer A is 3 to 30.
The thickness of the B layer is preferably 30 to 200μ, and the 0 layer is preferably about 3 to 100μ. However, as a matter of course, it is not limited to this.

The laminated structure of the present invention can further improve its properties and abrasion resistance by separately providing a preservation layer not containing graphite as the outermost layer, if necessary.

The protective layer for this purpose may be a synthetic resin layer having wear resistance, such as polyvinyl chloride, polymethyl methacrylate, polyethyl methacrylate, polyamide, ABS.
Those having a hardness of 80 degrees or more, such as resin or polyvinylidene chloride, are preferable.

The layers of the present invention can be applied by direct coating, transfer coating, gravure coating, calendaring, extrusion, etc., and the solvent can be removed by either wet or dry methods.

Further, in order to obtain the necessary film thickness, a coating method using multiple coatings can also be adopted.

The electromagnetic wave shielding property according to the present invention will be explained based on electric power as shown in FIG. If the input power of the electromagnetic wave is Pj and the reflected power is Pr, then the reflection coefficient R of the power is, and if the transmission coefficient of the power is T, then the power Pt of the electromagnetic wave after passing through the electromagnetic shielding material is If the power lost is Po, then PQ=Pi −Pr −Pt This is the electromagnetic wave that is converted into thermal energy without passing through the electromagnetic shielding material. moreover,
If the proportion of power lost, that is, the attenuation rate is A, then A--101o(] 10CPt/(Pi-Pr
) ] dB.

(Example) Hereinafter, the present invention will be explained according to Examples.

d'-3, the open part in the embodiment of the present invention means a weight part.

Example 1 Polyurethane resin Krisbon\B-635 (Dainippon Ink & Chemicals Co., Ltd.'!Sj>100 parts, Kish graphite powder (manufactured by Mitsukawa Seiko Co., Ltd.) 22 parts and dimethylformamide (hereinafter abbreviated as DMF). The solution was diluted with a mixed solvent of 1 part of methyl ethyl ketone (hereinafter abbreviated as MEK) to prepare a coating solution having a solution viscosity of 10 ooocps.

This was applied to 210 pieces of 75 denier polyester taffeta (see Table 1) at room temperature using a doctor knife and dried at 100'C for 1 minute to form a lower layer film with a solid content of 110 cI/m2. A coating solution with a solution viscosity of 20,000 cps was prepared by mixing 100 parts of Crisbon NB-635 with 110 parts of Quiche graphite powder and diluting D\-F2~iEK with a 1:1 mixed solvent, and rolling it on at room temperature. Coat the above with a knife coater and dry at 100°C for 1 minute, with solid content @ff112
0C]/m2, and further mixed polyurethane () or 100 parts of Crisbon NB-635, 10 parts of Quiche graphite powder, and DMF:MEK in a ratio of 1:1).
A solution resin diluted with a mixing solvent and having a solution viscosity of 10,000 cps was applied using the same coating method as the intermediate layer film. This was dried at 100°C for 1 minute, and the solid content adhesion ff1
A top layer film of 60 c+/m2 was formed, resulting in a three layer laminated coated fabric.

Furthermore, 100 parts of Rezaroid Lu-2027 (Dainichiseika Kogyo Co., Ltd. 1), epoxy-modified silicone oil, and Toure Silicone 5R-8411 (manufactured by Toure Silicone Co., Ltd.) were added to the 1q cloth as a top layer polyurethane surface treatment material. ) was diluted with MEK to obtain a solution viscosity of 12
A solution resin consisting of 0 cps was applied using a gravure roll coater at room temperature to form a solid content adhesion of 5i4 CJ/m2, and an electromagnetic wave shielding material having a water-repellent effect on the surface was obtained.

This electromagnetic shielding material had good water resistance of 90 points or more after 5 washes according to JISL-0844. In addition, as a result of shielding performance measurements for electromagnetic waves with a frequency of 6 to 12 GH2, as shown in Table 2, the electromagnetic wave shield has very good properties. A sheet-like material with properties was obtained.

Ratio shown in Table 1 and 2: Pα/ (Pi − Pr) Note 2) The above must be the average value within each frequency range (same article applies to Table 3) Example 2 Example 1 and A 1:1 mixture of 100 parts of polyurethane resin Crisbon NB-635, 10 parts of Quiche graphite powder, and DMF: and 'VIEK was applied to the same taffeta fabric with nickel metal plating with a film thickness of 0.5μ. A coating liquid diluted with a solvent and having a solution viscosity of 10,000C[)S was applied at room temperature. This was dried at 100° for 1 minute to form a lower layer film with a solid content of 15 g/m2. Next, polyurethane was added to 100 parts of 1 Nosbon NB-635, 100 parts of Quiche graphite powder, and 100 parts of DMF:MEK.
: Diluted with a mixed solvent of 1, solution viscosity 20,000 cps
A coating solution consisting of the following was applied at room temperature and dried at 100'C for 1 minute to form an upper layer film with a solid content of 500/m2.

Thereafter, 25% of the polymethacrylic ester was placed on the upper layer.
250% ethyl solution. /m- on the outermost layer, dried for 45 minutes, and then set at 160°C for 30 seconds to obtain 15 pieces with a surface hardness of 80°. The fabric-like electromagnetic shielding material obtained is 1Kg1000 according to JISK-6328.
No abnormalities were observed even after daily surface wear.

The electromagnetic wave shielding properties of this coated fabric were measured by irradiating electromagnetic waves of 6 to 12 Gf-1z to the side of the synthetic fat layer containing graphite powder. As shown in Table 3, the -stage It was confirmed that the transmittance decreased and the shielding effect improved. Therefore, if a shield box is made with the metal-plated side of this material on the outside, the electromagnetic waves inside the box will be absorbed and attenuated by the internal side walls, and the electromagnetic waves will not be radiated to the outside. Something that has an effect that does not penetrate into the body.
can.

Table 3 (Effects of the Invention) The electromagnetic shielding material according to the present invention has the flexibility of a fabric,
A part of the electromagnetic waves can be reflected, and the electromagnetic waves that are not reflected can be converted into active energy.

The electromagnetic shielding material according to the present invention maintains the characteristics shown in the figure, and can be widely used as various electromagnetic shielding materials, such as walls and curtains for electromagnetic clean rooms, cases for magnetic tapes, etc.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG.
FIG. 3 is a diagram showing graphite molecule drawing, and is a diagram illustrating electromagnetic shielding properties. 1... Electromagnetic wave shielding material 2... Area fiber base A... Electromagnetic wave shielding synthetic resin layer containing stabilizers, crosslinking agents, etc. for the purpose of adhesion B... Containing the largest amount of graphite Electromagnetic wave shielding synthetic resin layer C with a large electromagnetic wave shielding effect...An electromagnetic wave shielding synthetic resin layer for the purpose of protection with wear resistance and flexibility.

Claims (1)

[Claims] An electromagnetic shielding material characterized by being formed by directly or indirectly laminating a synthetic resin layer containing graphite powder on a fiber base material.