JPH0410595A - Electromagnetic shielding device - Google Patents

Abstract

PURPOSE:To obtain an electromagnetic wave shielding device which is elastic, flexible, excellent in usability, and able to block an electromagnetic wave wider in frequency band by a method wherein the electromagnetic shielding device is formed of a mixed material composed of ferrite powders specified in average grain diameter and frame-retardant rubber mixed at a specific ratio. CONSTITUTION:A mixed material composed of ferrite powder and flame- retardant rubber is formed into a right circular cylinder through an extrusion molding method, and the molded body is vulcanized into a shielding cylinder 21. Mn-Zn ferrite composed of 30-70% by weight of MnO, 10-40% by weight of ZnO, and 10-60% by weight of Fe2O3 is used. Ferrite is made to amount to 60-85% by weight in content. Ferrite powder is set to 3-15mum in average grain diameter. By this setup, an electromagnetic shielding device is excellent in shielding capacity, and able to block an electromagnetic wave wider in frequency band, especially an electromagnetic wave lower in frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides a method for blocking electromagnetic waves generated from various electronic devices and their accessory parts, and for blocking unnecessary electromagnetic waves entering from the outside. The present invention relates to an electromagnetic shielding device to be worn.

Conventional technology: 30 to 10 from accessories such as various electronic devices and cables
Electromagnetic waves in the 00 MHz band may be generated and invade the power lines, connection lines, etc. of other electronic devices, causing noise in the electronic devices. When such noise enters electronic equipment, the electronic equipment may malfunction or run out of control. To prevent this situation,
A shielding material for blocking electromagnetic waves is provided on the power supply line and the connection line.

A first conventional example of the shielding material is a sintered crystal of ferrite, which is hereinafter collectively referred to as a filter because of its function of removing noise. The filter 1 in FIG. 13 is called a ferrite core, has a rectangular parallelepiped shape, and has a through hole 3 through which the cable 2 is inserted. is wound around. That is, the filter 1 around which the cable 2 is wound constitutes a coil, and by appropriately determining the impedance of the filter 1, it functions as a filter that blocks noise in a predetermined frequency band.

A cylindrical sintered filter 1 as shown in FIG.
are called ferrite beads, and the cable 2 is inserted into the filter 1. The function is almost the same as the filter 1 shown in FIG. The filter 1 shown in FIG. 15 has half-split sintered bodies 4 and 5 that can be attached to and removed from each other, and the couple 2 is sandwiched between each of the sintered bodies 4 and 5. Even with such a configuration, noise components in the predetermined frequency band in the cable 2 can be absorbed.

In such a sintered ferrite crystal, desired noise attenuation characteristics can be satisfied by selecting the composition of the ferrite component, that is, multiple types of metal oxides.
Because products are sintered at temperatures above 00°C, they are rigid, and there are restrictions on the shapes and dimensions that can be manufactured, such as making it difficult to create complex shapes or large sizes, making it difficult to manufacture long products. It is. Another problem is that the manufacturing cost increases.

Another conventional example is to mix so-called soft ferrite into a thermoplastic polymer material and use the injection molding method as shown in Figures 13 to 15.
Molded into a core shape, bead shape, etc. as shown in the figure.

In such a molded product, in order to improve moldability, it is necessary to suppress the content of ferrite blended, and the noise damping effect will be lower than that of the sintered body of ferrite. In addition, in terms of formability, it is necessary to select the grain size of the ferrite within a relatively large numerical range, which also reduces the noise attenuation characteristics and makes the properties rigid, making it compatible with the shape of the attachment part of the cable. There are problems with low usability, such as difficulty in deforming the device. Another problem is that the frequency band of the noise to be removed is narrow due to the grain size and mixing amount of the ferrite.

Existing products, as shown in Japanese Patent Application Laid-Open No. 61-41202 "R Cable Shield Bead",
An attenuation effect of 10 dB to 30 dB is obtained in a frequency range of 1000. The state of such a damping effect is
This is shown in the graph of the attenuation characteristics described in the above-mentioned publication shown in FIG.

Line n21 in FIG. 16 is the case where only the cable is used, and line 122 is the case where the cable is covered with the molded product. on the other hand,
In such a conventional example, according to the experiment of the present inventor, 10
It was confirmed that there was almost no attenuation effect in the frequency band of 0 MHz to 500 MHz. That is, it is insufficient in blocking electromagnetic noise related to electronic equipment. In addition, such shielding materials are often used indoors, such as under floors or on walls, and are required to be flame retardant, but the olefin-based plastic described in the above-mentioned publication has the problem of lacking flame retardancy. be.

A third conventional example is a shielding cylinder 11 shown in FIG.

Such a shielding cylinder 11 is called a zipper tube, and is made of a polyvinyl chloride (vinyl chloride) film 8 and a net-like structure of fine wires made of metalized fibers or metal materials for shielding signals from the outside. The net-like cylinder 9 is formed of a member having the surface of ordinary fibers subjected to metal plating or sputtering of a metal substance, and is fixed to the film 8. The cable 2 is coated with this. This conventional example has a problem in that electromagnetic waves may leak through the fiber mesh and enter the cable 2 or be radiated from the cable 2.

The fourth conventional example includes a structure in which a thin film of metal such as aluminum or copper is vapor-deposited on one surface of a synthetic resin film such as PET (polyethylene terephthalate) film, and an adhesive is applied to the other surface. conductive tape made of synthetic resin material with The configuration of this conventional example is similar to the conventional example shown in FIG. Referring to FIG. 17, a metal thin film 9a is formed on one surface of film 8, and an adhesive layer 10 is formed on the other surface, forming a sheet-like body 11a.

In such a conventional sheet-like body 11a, the cable 2 is wound around the cable 2, and both ends in the circumferential direction are adhered with the adhesive layer 10. In the sheet-like body 11a of the conventional example, when the sheet-like body 11a is wound around the cable 2, electromagnetic waves leak or invade the overlapping portions near both ends of the sheet-like body 11a in the circumferential direction.

Further, even if the sheet-like body 11a is in the form of a sheet or a band, when such a member is attached to the cable 2 in a relatively narrow space such as under the floor,
There is a problem with poor workability. Also, the sheet-like body 11a
Depending on the material of the film 8 constituting the film, there is a certain degree of flame retardancy as described above.

Problems to be Solved by the Invention As mentioned above, each of the conventional examples has the problem that they are relatively rigid and have poor usability, and those that are flexible have poor flame retardancy. In addition, in terms of formability, it is not possible to increase the amount of ferrite mixed or reduce the particle size, and the noise band that can be absorbed is limited, and the electromagnetic wave shielding effect is insufficient. Ta.

An object of the present invention is to solve the above-mentioned technical problems and provide an electromagnetic wave shielding device that has elasticity and flexibility, is easy to use, and has a significantly wide frequency band of shielded electromagnetic waves. It is.

Means for Solving the Problems The present invention provides ferrite powder with an average particle size of 3 to 15 μm.
~85% by weight and 40-15% by weight of flame-retardant rubber
An electromagnetic wave shielding device characterized in that it is made of a mixed material containing. An electromagnetic wave shielding device may be constructed by forming a net-like covering layer made of thin metal wires on the outer surface of the structure made of this mixed material. This conductive coating layer is a network formed of conductive thin wires, and the conductive thin wires are made of a metal such as aluminum, copper, iron, steel, etc., and are knitted together. This is achieved by

The ferrite in the present invention has an initial magnetic permeability μ. Those with relatively high values are selected. Such ferrite is Mn-
The ferrite used is a Zn-based ferrite, which has the characteristics of flexibility, flame retardance, and wide noise absorption band, which are the characteristics of the present invention. This Mn-Zn ferrite is MnO30
~70 wt%, Zn010~40 wt% and Fe20
It is characterized by containing 310-60% of heavy background. A ferrite having such a composition exhibits an effect exceeding a predetermined level on magnetic loss over a band of 30 MHz to 100,100 O.

Typical synthetic rubbers for the flame-retardant rubber include chloroprene rubber, chlorosulfonated polyethylene, and chlorinated polyethylene. Other examples of rubber containing flame retardants include:

As for the types of rubber, all synthetic rubbers can be used, including natural rubber, ethylene propylene rubber, styrene butadiene rubber, butadiene rubber, acrylonitrile butadiene copolymer rubber, hydrogenated rubber thereof, and polyisoprene rubber. .

Flame retardants include brominated flame retardants, chlorinated flame retardants, and inorganic flame retardants. As the brominated flame retardant, hexabromobenzene, hexabromo biphenyl ether, tribromophenol, tetrabromobisphenol A, etc. are used. As the chlorinated flame retardant, chlorinated paraffin, chlorinated polyethylene, etc. are used. Inorganic flame retardants include antimony dioxide, sodium antimony, zirconium compounds, aluminum hydroxide, and boron compounds.

In producing the flame-retardant rubber, the mixed material is manufactured by extrusion molding rather than by injection molding as described in the prior art section. This allows the content and particle size of the ferrite powder to be increased,
Electromagnetic wave shielding performance and processability during manufacturing are improved. In other words, extrusion molding does not require fluidity as much as injection molding, so if the mixture is kneaded so that the distribution density is uniform and extrusion molding is performed, the composition will be uniformly dispersed and the surface texture will be fine. A good molded product can be obtained.

Through such extrusion molding, a cylindrical electromagnetic shielding device is formed. Such an electromagnetic wave shielding device can cover the power cables and connection cables of various electronic devices over a desired length. This makes it possible to prevent electromagnetic waves from leaking out or entering even if the cable is covered, as explained in the section on the prior art.

Function As described above, according to the present invention, an electromagnetic shielding device is formed from a mixed material containing ferrite powder and flame-retardant rubber. Such an electromagnetic wave shielding device has flame retardancy, relatively flexibility, and is easy to process, and the particle size and I content of the ferrite powder are relatively increased, so it can be shielded. Expand the frequency band of electromagnetic waves. In particular, it will expand to relatively low frequency bands.

Forming a net-like coating layer made of fine metal wires on the outer surface of the cylindrical body made of the mixed material can shield electromagnetic waves and prevent the intrusion of harmful electromagnetic waves without impairing the flexibility of the mixed material. The effect can be improved.

The ferrite constituting the mixed material is a Mn-Zn ferrite, and has a significantly improved electromagnetic wave shielding effect. The flame-retardant rubber constituting the mixed material is preferably proproprene rubber, which itself is flame-retardant, and in other cases, various synthetic rubbers vulcanized with a flame retardant as described above, or Natural rubber is also used. Carbon black may be added to the above-mentioned flame retardant rubber as a reinforcing agent.

If the ferrite powder content is less than 60%, the electromagnetic wave shielding effect will be reduced, and especially the shielding effect in a relatively low frequency band will be lost. On the other hand, ferrite powder weighs 85? . If it exceeds this, the material becomes physically brittle and the flexibility, which is a feature of the present invention, is lost.

If the average particle size of the ferrite powder is less than 3 μm, the electromagnetic wave shielding effect will be reduced, and if it is more than 15 μm, the powder will become physically brittle, resulting in uneven mixing and poor moldability.

Embodiment FIG. 1 shows an electromagnetic wave shielding device according to an embodiment of the present invention.
FIG. 3 is a perspective view of the shielding cylinder 21. FIG. For example, the shielding cylinder 21 is formed into a right cylindrical shape with an inner diameter dl, an outer diameter d2, and a length Ll, and the diameters d1, d2, and length Ll are, for example, selected to be 10 mm, 20 mm, and 1000 mm, respectively.

As will be described later, the shielding cylinder 21 of this embodiment has a shielding effect on electromagnetic waves in a wide frequency band, and is flexible and flame retardant.

Such a shielding cylinder 21 is made of flame-retardant synthetic rubber or natural rubber. Examples of synthetic rubber include chlorobutone rubber and chlorosulfonated polyethylene (CS M
), chlorinated polyethylene (CPE), etc., or ethylene propylene rubber mixed with a flame retardant described below, styrene butadiene rubber, butadiene rubber, acrylonitrile butadiene copolymer rubber, hydrogenated rubber thereof, polyisobutylene rubber, etc. All synthetic rubbers including rubber can be used.

Flame retardants include brominated flame retardants, chlorinated flame retardants, and inorganic flame retardants. As the brominated flame retardant, hexabromobenzene, hexabromo biphenyl ether, tribromophenol, tetrabromobisphenol A, etc. are used. As the chlorinated flame retardant, chlorinated paraffin, chlorinated polyethylene, etc. are used. Inorganic flame retardants include antimony trioxide, sodium antimony, zirconium compounds, aluminum hydroxide, and boron compounds. Carbon black is blended as a reinforcing agent into such flame retardant rubber, ferrite powder is mixed therein, and the mixed wire rubber is extruded into a cylindrical shape using a rubber extruder and vulcanized. In this way, the shielding cylinder 21 shown in the first diagram is obtained.

Electromagnetic waves leaked from ordinary electronic devices range from 30MHz to 1
The frequency band is 000 MHz, and Mn-Zn ferrite is a ferromagnetic material that has a large magnetic loss in this frequency band. Such MnZn-based ferrite preferably contains 30 to 70% by weight of MnO and 10 to 4% by weight of ZnO.
A ferrite having a composition of 0% by weight and 10 to 60% by weight of Fe203 is used. In order to maintain the magnetic loss effect of the ferrite itself relatively high and not impair the strength of the flame-retardant rubber, ferrite having an average particle size of 3 μm to 15 μm is used. The kneaded rubber mixed with such ferrite powder is extruded into a cylindrical shape using a rubber extruder as described above, and is vulcanized to form the shielding cylindrical body 21.

FIG. 2 is a perspective view of a shielding cylinder 21a according to a second embodiment of the present invention. The shielding cylinder 21a of this embodiment is, for example, a first
The shielding cylinder 21 shown in the figure includes a cylinder main body 22 and a covering body 23 having a similar shape and similar component composition. The covering body 23 is made of linear metal material such as aluminum, iron, stainless steel, etc., knitted in a bias knitting manner.
The obtained net-like body is used as the covering body 23. Therefore, the covering body 23 can improve the effect of shielding electromagnetic waves and the effect of preventing the intrusion of interfering radio waves without impairing the flexibility of the cylindrical body 22 described in the above embodiment.

FIG. 4 is a system diagram showing the overall configuration of the computer main body 25 including the printer 24. As shown in FIG. Computer body 25
is connected via a connector 29 to the other end of the power cable 26 whose one end is connected to the plug 28 . Further, the printer 24 is connected to the computer main body 25 via a connection cable 27 having connectors 31 and 32 connected to both ends.

Computer body 25, printer 24, power cable 2
6. Electromagnetic waves are radiated into the air from the connection cable 27 and the connectors 2931.32, as shown by arrows in FIG.

The shielding cylinder 21.21a of this embodiment is connected to the power cable 26.
This is intended to shield electromagnetic waves generated and leaked along the entire length of the connection cable 27, and the connector 29
32 and the connecting cable 27 are also intended to shield locally generated electromagnetic waves.

FIG. 5 is a graph explaining the magnetic properties of the ferrite used in this example.6 Considering that the ferrite used in this example has a relatively low strength of the magnetic field H of the electromagnetic waves to be shielded, In order to absorb electromagnetic waves of such intensity well, the change curve 115 of the magnetic flux density B of ferrite,
Initial permeability μ at 116,117. It is preferable that the shielding cylinder 21.21a of this embodiment, which is used for shielding electromagnetic waves in an environment where electromagnetic waves are radiated, is as large as possible. It is desirable that the residual magnetic flux density Br be O or as small as possible so as not to cause the above-mentioned initial magnetic permeability μ. The residual magnetic flux density Br is only required from the viewpoint of practical usability of the shielding cylinder 21.21a of the present embodiment, and has no particular relation to the essence of the present invention.

FIG. 6 is a system diagram of a configuration for measuring the electromagnetic wave shielding characteristics of the shielding cylinder 21.21a. The measurement of the shielding characteristics is carried out using a signal generator 33 that can generate a signal with a predetermined waveform over a predetermined frequency range;
A signal analyzer 34 is connected to the connecting cable 27 via the connecting cable 27 to observe the state in which a signal supplied from one end of the connecting cable 27 by the signal generator 33 appears at the other end of the connecting cable 27. .

Several experimental examples of the shielding cylinder 21 are shown below. In this experimental example, the average particle size and specific gravity of the ferrite are as shown in Table 1 below, and the composition of the matrix rubber, which is a mixture of chloroprene rubber and a plurality of additives, is as shown in Table 2 below.

(The following is a blank space) Based on the 6301 standard, the strength at break and the elongation at break were measured. The second test measures the ease with which the obtained shielding cylinder 21 can be cut with scissors, a knife, etc., and its flexibility. As a criterion for evaluating flexibility, the well-known elongation at break 100? Adopt δ.

Table 3 Using the ferrite and matrix rubber thus obtained, a mixture having the composition ratio of the five examples shown in Table 3 below was formed, and this mixture was extruded into a right cylindrical shape and vulcanized. A shielding cylinder 21 was formed. For this shielding cylinder 21, 100 parts by weight of matrix rubber having the composition shown in Table 2 of Japanese Industrial Standard JISK Example 1 and 160 parts by weight of ferrite having the composition shown in Table 1 (62 parts by weight) were added.
) was used to manufacture the shielding cylinder 21 shown in the first figure. When the physical properties of the shielding cylinder 21 in this example were tested, the strength at break was 43 kg, cm, and the elongation at break was 270?5. This means that a shielding cylinder 21 with relatively flexible physical properties was obtained. Regarding this shielding Fi and the electromagnetic wave shielding ability of the cylinder 21, the sixth
[As a result of conducting a test using the test method described with reference to 2I, a graph as shown in FIG. 7 was obtained. The line 11 in FIG. 7 indicates the connecting cable 2 without the shielding cylinder 21 attached.
Line 12 shows the result when the shielding cylinder 21 is attached to the connection cable 27.

In other words, when the shielding cylinder 2) is attached, the signal attenuation starts to become larger at around 200MHz than when the connecting cable 27 is used alone, and it is about 10dBcr around 400MHz.
) shows an increase in d display. This is because the degree of shielding of electromagnetic waves has increased, compared to the attenuation characteristics of the conventional example shown in Fig. 16, in which the degree of IJ attenuation becomes greater than that of the case of only cables only when the frequency exceeds 600 MHz.
Moreover, the band is expanding to the lower frequency side.

Example 2 A shielding cylinder 21 was manufactured using a mixture of 100 parts by weight of matrix rubber having the composition shown in Table 2 and 300 parts by weight (75% by weight) of ferrite having the composition shown in Table 1. A test with characteristics similar to those in the example was conducted. Strength at break is 43k
g/cm2, and the elongation at break was 215%. It can be seen that relatively flexible physical properties are obtained in this case as well. In addition, the signal attenuation test was conducted in the same manner as in the first embodiment.
The results are shown in the graph of FIG. Line 11 in Figure 7 is only connected to the connection cable 27, and line 1
4 is a case where the shielding cylinder 21 is attached to the cable 27.

In this embodiment, the effect of signal attenuation by the shielding cylinder 21 appears from around 100 MHz, and the effect gradually increases as the frequency increases. Compared to the conventional example, this example also exhibits a characteristic of absorbing electromagnetic waves much better in the lower frequency band side.

Example 3 100 parts by weight of matrix rubber having the composition shown in Table 2 and
550 parts by weight (85% by weight) of ferrite having the composition shown in the table
The shielding cylinder 21 was manufactured using the following. This shielding cylinder 2
1 was subjected to physical property tests similar to those in the above example.

According to this, the strength at break is 22 kg/cm
2, and the elongation at break was 140%. This case also shows relatively good flexibility. On the other hand, the results of the test regarding absorption of electromagnetic waves are shown in the graph of FIG.

Line 15 is the case where only the connection cable 27 is used, and line 16 is the case where the cable is covered with the shielding cylinder 21. In this example, absorption of electromagnetic waves by the shielding cylinder 21 can be seen from around 50 MHz, and as the frequency increases, the absorption effect increases rapidly. This shows an increase in attenuation of about 10 dB.

Comparison 13'lJ 1 100 parts by weight of matrix rubber having the composition shown in Table 2 and
100 parts by weight (50% by weight) of ferrite having the composition shown in the table
A shielding cylinder was formed using Formed shielding cylinder 21
When the physical properties were tested as described above, the strength at break was 100 kg/cmz, and the elongation at break was 350%.

This shows that the physical properties are softer and stronger than those of Examples 1 to 3. On the other hand, when a test regarding the absorption of electromagnetic waves was conducted, the results were as shown in FIG. Line 17 in FIG. 10 shows the case where only the connection cable 27 is used, and line 18 shows the case where the shielding cylinder is attached. In this comparative example, the shielding cylinder 21
Although the electromagnetic wave absorption effect starts to appear, the extent is minute, about several dB around 700 MHz to 800 MHz. That is, it can be seen that when the content of ferrite in the shielding cylinder 21 is less than 60%, the electromagnetic wave absorption performance is significantly reduced.

Comparison 2 A shielding cylinder was formed from 100 parts by weight of the matrix rubber shown in Table 2 and 650 parts by weight (87% by weight) of ferrite. When this shielding cylinder was subjected to the same physical property test as in the above example, the strength at break was 16 kg/cm 2 and the elongation at break was 90%. In this comparative example,
Flexibility is severely lost, and if the shielding cylinder 21 is bent, it will break.

From the above Examples 1 to 3 and Comparative Examples 1 and 2, it can be seen that in forming the shielding cylinder 21 of the present invention, it is desirable that the ferrite content be selected in the range of 60 to 85% by weight. Regarding the particle size of ferrite, according to experiments conducted by the present inventor, if the particle size exceeds 15 μm, uneven dispersion of ferrite in the matrix rubber occurs during extrusion molding, the surface texture becomes tree-ring-like, and It was confirmed that the physical properties became brittle and the moldability deteriorated.

When the particle size was less than 3 μm, the electromagnetic wave absorption test as described above was performed, and compared to the case of only the connection cable,
Absorption performance of 4 to 6 dB was not observed in the frequency band of 200 to 400 MHz, and 500 MHz to 1000 M
Attenuation of 20-50 dB was observed in the Hz frequency band.

Therefore, the performance is extremely insufficient in terms of expanding the signal frequency band to be shielded, which is one of the objectives of the present invention, and especially extending to the low frequency region. Therefore, it is desirable that the average grain size of ferrite is selected within the range of 3 to 15 μm.

The inventor of the present invention conducted a flame retardancy test on the flame retardant rubber used in the present invention in accordance with the Japanese Industrial Standard JIS K 6324. This is a test in which a sample is placed in the flame of a burner for a predetermined period of time, the flame is removed, and then the duration of the flame from the sample is measured, and if the duration is less than 1 minute, it is evaluated as flame retardant. The samples used were Examples 4 to 7 and Comparative Example 3 shown in Table 4 below.

(Left below) Table 4 CR-chloroprene rubber, C5M-chlorosulfonated polyethylene, 5BR=styrene-butadiene rubber, CPE
- Chlorinated polyethylene As shown in the experimental results in Table 4, it was confirmed that all the rubbers of Examples 4 to 7 had flame retardancy.

Although the manufacturing conditions for the shielding cylinder 21 shown in FIG. 1 were set as described above, in order to further improve the electromagnetic wave shielding ability achieved by the shielding cylinder 21, the manufacturing conditions for the shielding cylinder 21 as shown in FIG.
Form 1a. The shielding cylinder 21a is, for example, the second
100 parts by weight of matrix rubber having the composition shown in Table 1 and 400 parts by weight (80% by weight) of ferrite having the composition shown in Table 1
The cylinder body 22 was formed from the above. Regarding the cylinder body 22, when the physical property tests explained in each of the above examples were conducted, the strength at break was 31 kg, cm2, and the elongation at break was 180.
9o, and it was confirmed that it had good flexibility.

With respect to such a cylinder body 22, the net angle is 54 degrees, the wire diameter is 02
The edge material was covered with a net-like covering 23 made of copper, aluminum, steel wire (zinc chromate plating), stainless steel, etc. to form a shielding cylinder 21a. Regarding such a shielding cylinder 21a, the electromagnetic wave absorption performance as described in each of the above-mentioned Examples was tested. The results are shown in FIG. 11th
Line 19 in the figure is for only the connection cable 27,
Line 110 shows the case where the connection cable 27 is covered only with the cylindrical body 22, line β11 shows the case where the connection cable 27 is covered with the shielding cylindrical body 21a, and line 112 shows the case where the connection cable 27 is covered with the shielding cylindrical body 21a. This is also the case when the covering body 23 is grounded.

In this example, it can be seen that the degree of electromagnetic wave absorption is greater when the cylinder body 22 is covered with the covering body 23, and in the case of line 111, the electromagnetic wave absorption effect of the shielding cylinder 21a appears from around 100 MHz.

As mentioned above, each of the examples has flame retardancy, is flexible, has greater electromagnetic wave absorption performance than conventional products, and has expanded the frequency band of the absorbed signal, further extending to the low frequency band side. A shielding cylinder 21.21a was obtained. Further, the shielding cylinder 21 and the cylinder body 22 provided with the covering body 23 are relatively flexible, and can be easily manufactured into a relatively long length as shown in FIG. If necessary, the power cable 26 and the connection cable 27 can be covered over their entire length, and noise radiation and intrusion can be effectively prevented.

Further, the shielding cylinder 21 is flexible and can cover parts such as the plug 28 and the connectors 29 to 32 that have a larger diameter or are more deformed than the connecting cable 27. Further, since the shielding cylinder 21 can be manufactured in a long length, such a shielding cylinder can be cut to a length necessary for the work with a cutter or scissors as appropriate for construction. In this respect, the shielding cylinder 21 is extremely usable.

Although the present invention has been described as a cylindrical shielding body 21.21a, the embodiments of the present invention are not limited to such a cylindrical body, but may be realized as a planar sheet body or a band-like body. Furthermore, another example is shown in FIG. A plurality of lead wires used to connect the computer main body and a printer, etc. are arranged in parallel with each other using a synthetic resin material, and the multi-core cable 25 is molded into a belt shape. A shielding cylinder 26 is used which is formed so that its cross section perpendicular to the direction has a flat rectangular annular shape.

Further, the material forming the electromagnetic wave shielding device of the present invention is not limited to the above embodiments, but includes a wide range of modifications within the spirit of the present invention.

Effects of the Invention As described above, according to the present invention, not only good shielding ability is obtained, but also the frequency band of electromagnetic waves to be shielded is expanded.
Moreover, it is expanded to the low frequency band side. This significantly improves electromagnetic wave shielding performance. Further, the electromagnetic wave shielding device of the present invention is flexible and flame retardant, and has versatility depending on the shape of the object to be constructed. Moreover, even when used indoors, it is safe to use fire protection.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a shielding cylinder 21 according to an embodiment of the present invention, FIG. 2 is a perspective view of a shielding cylinder 21a, and FIG. 3 is a sectional view taken from the section line ■-■ in FIG. , FIG. 4 is a system diagram explaining the field of application of the present invention, FIG. 5 is a graph explaining the magnetic properties of ferrite used in the present invention, and FIG. 6 is a configuration for testing electromagnetic wave absorption performance in the present invention. Family tree, No. 7
9 to 9 are graphs explaining the electromagnetic wave absorption performance of each example of the present invention, FIG. 10 is a graph explaining the electromagnetic wave absorption performance of Comparative Example 1, and FIG. 11 is a graph explaining the electromagnetic wave absorption performance of the shielding cylinder 21a. Graphs to be explained; FIG. 12 is a perspective view of a shielding cylinder 26 according to yet another embodiment of the present invention; FIGS. FIG. 16 is a graph illustrating the electromagnetic wave absorption performance of the conventional example, and FIG. 17 is a perspective view illustrating the configuration of another conventional example. 21.21a, 26・Shielding cylinder body, 22・Cylinder body, 23・
・Coating, 26...Power cable, 27...Connection cable, 28 Plug, 29-32...Connector agent Patent attorney Number of strokes Keibu 1st wJ 6E ・1 Figure Figure 9 Horse water ridge (MHz) ) 111! (MHz) 27 Figure! lj number (MHz) Darkness l (MHz) 11 Figure 13 Figure 15 Figure\1 Figure 14 11, lla litai (MHz) Figure 16

Claims (7)

[Claims] (1) Ferrite powder 60-8 with an average particle size of 3-15 μm
An electromagnetic shielding device comprising a mixed material containing 5% by weight of rubber and 40 to 15% by weight of flame-retardant rubber. (2) The electromagnetic wave shielding device according to claim 1, wherein a net-like coating layer made of thin metal wires is formed on the outer surface. (3) The electromagnetic wave shielding device according to claim 1, wherein the ferrite is a Mn-Zn ferrite. (4) Mn-Zn ferrite contains 30 to 70% by weight of MnO, 10 to 40% by weight of ZnO, and Fe_2O_31
The electromagnetic wave shielding device according to claim 1, characterized in that the electromagnetic wave shielding device contains 0 to 60% by weight. (5) The electromagnetic wave shielding device according to claim 1, wherein the flame-retardant rubber is selected from chloroprene rubber, chlorosulfonated polyethylene rubber, and chlorinated polyethylene rubber. (6) The electromagnetic wave shielding device according to claim 1, wherein the flame-retardant rubber is natural rubber and/or synthetic rubber that is vulcanized with a flame retardant. (7) The electromagnetic wave shielding device according to claim 1, characterized in that it is formed into a cylindrical shape from the mixed material.