JP2003142867A - Electromagnetic wave shielding gasket and electromagnetic wave shielding case - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new electromagnetic wave shielding gasket that can be reduced in size and has a good electromagnetic wave shielding property. SOLUTION: This electromagnetic wave shielding gasket 30 is interposed between two electromagnetic wave shielding case members 10 and 20 so as to shield electromagnetic waves passing through the gap between the members 10 and 20. This gasket 30 has a base material 31 which is composed mainly of a first elastic material, and seals the gap between the members 10 and 20 by blocking the gap, and an electromagnetic wave shielding coating member 32 which contains the base material 31, a second elastic material; and a conductive fibrous filler 32a scattered in the second elastic material and oriented in the coupling direction of the case members 10 and 20, and is formed to cover at least one shielding surface of the base material 31 blocking the gap between the case members 10 and 20. Since the filler 32a is oriented in the coupling direction of the members 10 and 20, the electromagnetic waves passing through the gap between the members 10 and 20 can be shielded.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an electromagnetic wave shielding gasket and an electromagnetic wave shielding case.

[0002]

2. Description of the Related Art An electromagnetic wave shielding gasket is generally used in a gap between case members constituting an electromagnetic wave shielding case or the like. Therefore, in the same way as a normal gasket, by maintaining the airtightness and watertightness between these case members, the role of preventing moisture and dust from entering the inside of the electromagnetic wave shielding case, as well as the electromagnetic waves that penetrate the gaps between the case members. It must play a role in blocking passage.

In this case, in order to provide the gasket with an electromagnetic wave shielding performance of shielding passage of electromagnetic waves, a method of mixing an electromagnetic wave shielding material such as carbon fiber, metal fiber or zinc white into an elastic material such as a rubber material used for the gasket. Has been taken. However, if a large amount of electromagnetic wave shielding material is mixed with an elastic material such as a rubber material in order to improve the electromagnetic wave shielding performance, the elasticity of the rubber material is significantly impaired and the deformation cannot be recovered. As a result, there has been a problem that the watertightness and airtightness required for the gasket cannot be secured.

[0004]

Therefore, an electromagnetic wave shielding gasket having watertightness and airtightness as well as electromagnetic wave shielding performance is disclosed in, for example, Japanese Patent Laid-Open No. 2001-1606.
Japanese Unexamined Patent Publication No. 97 discloses a gasket formed by combining an electromagnetic wave shielding rubber and a highly elastic rubber. In this electromagnetic wave sealing gasket, the highly elastic rubber plays a role of maintaining airtightness and watertightness, and the electromagnetic wave shielding rubber plays a role of blocking passage of electromagnetic waves.

As described above, a method has been developed in which different members share the role of maintaining watertightness and airtightness and the role of blocking passage of electromagnetic waves. However, in order to improve the electromagnetic wave shielding performance by taking a method of constructing the member that plays a role of blocking the passage of electromagnetic waves in this way in combination with the member that plays a role of maintaining watertightness and airtightness, A member that plays a role of blocking passage becomes large. As a result, the size of the entire electromagnetic wave shielding gasket becomes large.

However, under the circumstances of high performance and diversification of electronic parts, functional failures due to electromagnetic waves are becoming complicated and diversified. Therefore, the electromagnetic wave shielding gasket is used in various places of various shapes of electromagnetic wave shielding cases. Therefore, if the shape of the electromagnetic wave shielding gasket is large, it becomes difficult to use it in various places of the electromagnetic wave shielding case.

Therefore, an object of the present invention is to provide a new electromagnetic wave shielding gasket which can be miniaturized and has a good electromagnetic wave shielding performance.

Another object of the present invention is to provide an electromagnetic wave shielding case equipped with a new electromagnetic wave shielding gasket which can be miniaturized and has good electromagnetic wave shielding performance.

[0009]

Means for Solving the Problem and Its Action (First Invention: Electromagnetic Wave Shield Gasket) The electromagnetic wave shield gasket of the first invention for solving the above problem is interposed between two electromagnetic wave shielding case members. In the gasket for electromagnetic wave shielding, which seals the gap between the two electromagnetic wave shielding case members and shields electromagnetic waves from passing through the gap, the first elastic material is mainly used to block and seal the gap. A base material, a second elastic material, and a conductive fibrous filler dispersed in the second elastic material and oriented in a direction connecting the two electromagnetic wave shielding case members, and interrupting the gap of the base material. And an electromagnetic wave shield coating member coated on at least one shield surface.

Since the base material has a sufficient elasticity mainly by the first elastic material and seals by blocking the gap, it tightly adheres so that no gap is formed between the two electromagnetic wave shielding case members. And the watertightness can be secured. Again 2
Even if the gaps between the two electromagnetic wave shielding case members have various shapes, it is possible to sufficiently cope with them.

The electromagnetic wave shield covering member includes a second elastic material and a conductive fibrous filler dispersed in the second elastic material and oriented in a direction connecting the two electromagnetic wave shielding case members. The conductive fibrous filler is oriented in the direction connecting the two electromagnetic wave shielding case members to form a second
Since it is dispersed in the elastic material, the electromagnetic wave shielding performance can be improved as compared with the case where it is simply dispersed. Since the electromagnetic wave shield covering member is covered by at least one shield surface that shields the gap between the two electromagnetic wave shielding case members out of the surfaces of the base material, the electromagnetic wave passing through this gap is prevented. Can be shielded.

(Second invention: electromagnetic wave shielding case)
An electromagnetic wave shielding case according to a second aspect of the present invention, which solves the above-mentioned problems, is provided between at least two electromagnetic wave shielding case members and two electromagnetic wave shielding case members to seal a gap between the two electromagnetic wave shielding case members. In an electromagnetic wave shielding case having a gasket for electromagnetic wave shielding that stops and shields electromagnetic waves from passing through the gap, the electromagnetic wave shielding gasket mainly comprises a first elastic material to block and seal the gap. A base material, a second elastic material, and a conductive fibrous filler dispersed in the second elastic material and oriented in a direction connecting the two electromagnetic wave shielding case members, and blocking the gap of the base material. And an electromagnetic wave shield coating member coated on at least one shield surface.

The electromagnetic wave shielding case is interposed between the two electromagnetic wave shielding case members to seal a gap between the two electromagnetic wave shielding case members and to shield electromagnetic waves from passing through the gap. Since it has the electromagnetic wave shielding gasket, the two electromagnetic wave shielding case members can be tightly adhered to each other so that there is no space between them, and the airtightness and watertightness can be surely secured. It can have various shapes. Further, the electromagnetic wave shielding performance can be improved as compared with the conventional electromagnetic wave shielding gasket in which the conductive fibrous filler is simply dispersed.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION (First Invention: Electromagnetic Wave Shield Gasket) Structure The first electromagnetic wave shield gasket of the first invention is interposed between two electromagnetic wave shield case members to form two electromagnetic wave shield case members. An electromagnetic wave shielding gasket (hereinafter, appropriately abbreviated as "gasket") that seals the gap and shields electromagnetic waves from passing through this gap.

This gasket has a base material and an electromagnetic wave shield coating member that covers at least one shield surface that shields a gap between two electromagnetic wave shield members of the surface of the base material.

The base material is mainly composed of the first elastic material and blocks the gap between the two electromagnetic wave shielding members to seal them. As the first elastic material, crosslinked rubber such as synthetic rubber and natural rubber, and uncrosslinked thermoplastic elastomer can be used. Specifically, styrene butadiene rubber (SBR),
Butadiene rubber (BR), ethylene propylene rubber (E
Examples thereof include PM, EPDM), fluororubber (FKM), acrylic rubber (ACM), silicone rubber (VMQ), and natural rubber. As the first elastic material, a material suitable for the environment in which the electromagnetic shielding gasket is used can be selected.

Further, to the first elastic material, a reinforcing material such as carbon black, a vulcanization aid such as zinc oxide, a softening agent, an antiaging agent, etc. may be used as long as the elasticity required as a base material is not impaired. Can be added appropriately.

As described above, since the base material of the electromagnetic wave sealing gasket is mainly composed of the elastic first elastic material, the electromagnetic wave shielding gasket is closely adhered to the portion to be used, and the gap between the two electromagnetic wave shielding members is kept close. By blocking and sealing, the airtightness and watertightness of this gap can be secured.

The electromagnetic wave shield coating member is coated on at least one shield surface which shields a gap between two electromagnetic wave shield members of the base material. By covering the shielding surface with the electromagnetic wave shield coating member, it is possible to shield the electromagnetic waves that try to pass through the gap. In this case, it is preferable to cover the side surface of the base material on the inner space side surrounded by the electromagnetic wave shielding case member, that is, the side surface of the base material on the inner side with the electromagnetic wave shield coating member. When the electromagnetic wave shield coating member is coated on the outer side surface of the base material, it is exposed to moisture or the like in the outside air and is easily deteriorated.

It is preferable that both ends of the electromagnetic wave shield covering member are in contact with two electromagnetic wave shield case members forming a gap. In this way, the electromagnetic wave seal covering member comes into contact with the two electromagnetic wave shield case members, so that the electromagnetic wave shield performance can be ensured.

The electromagnetic wave shield covering member includes a second elastic material and a conductive fibrous filler dispersed in the second elastic material. This electromagnetic wave shield covering member has a structure in which a conductive fibrous filler is dispersed in a second elastic material serving as a matrix.

This conductive fibrous filler constitutes a gap in which the electromagnetic shielding gasket of the present invention is used. 2
It is oriented in a direction connecting the two electromagnetic wave shielding case members. Here, that the conductive fibrous filler is oriented in the direction connecting the two electromagnetic wave shielding case members means that the gap between the two electromagnetic wave shielding case members is from one side to the other side. It means that it is perpendicular to the traveling direction of the electromagnetic wave when passing through.

Generally, when an electromagnetic wave passes through a gap between two conductors from one side to the other side, the electromagnetic wave whose vibration direction is parallel to the direction connecting the two conductors is restricted. Become. In other words, the vibration direction of the electromagnetic wave is 2
Electromagnetic waves perpendicular to the direction in which the gap between the two conductors extends will be restricted from passing. Electromagnetic waves whose vibration direction is perpendicular to the direction connecting the two conductors can pass through the gap. In other words, electromagnetic waves whose vibration direction is parallel to the direction in which the gap between the two conductors extends can pass through the gap. Therefore, even in the gap between the two electromagnetic wave shielding case members in which the electromagnetic wave shielding gasket of the present invention is used, the two electromagnetic wave shielding case members are
Electromagnetic waves whose vibration direction is parallel to the direction connecting the two electromagnetic wave shielding case members are originally restricted from passing through this gap. An electromagnetic wave whose vibration direction is perpendicular to the direction connecting the two electromagnetic wave shielding case members generally passes through the gap between the two electromagnetic wave shielding case members without being shielded by the two electromagnetic wave shielding case members. It will be possible.

However, since the electromagnetic wave shielding gasket of the present invention has the electromagnetic wave shielding covering member configured so that the conductive fibrous filler is oriented in the direction connecting the two electromagnetic wave shielding case members in this gap, the electromagnetic wave shielding covering member is formed. Electromagnetic waves whose vibration direction is perpendicular to the direction connecting the two electromagnetic wave shielding case members are restricted from passing through this gap.

By thus orienting the conductive fibrous filler dispersed in the electromagnetic wave shield covering member in the direction connecting the two electromagnetic wave shield case members, the electromagnetic wave shield performance can be improved.

The second elastic material used as the matrix of the electromagnetic wave shield covering member is, like the first elastic material, an elastic crosslinked rubber such as synthetic rubber or natural rubber, and an uncrosslinked thermoplastic elastomer. Can be used. Specifically, styrene butadiene rubber (SB
R), butadiene rubber (BR), ethylene propylene rubber (EPM, EPDM), fluororubber (FKM), acrylic rubber (ACM), silicone rubber (VMQ), natural rubber and the like. As the second elastic material, a material suitable for the environment in which the electromagnetic shield gasket is used can be selected. Further, a reinforcing material such as carbon black, a vulcanization aid such as zinc oxide, a softening agent and an antiaging agent can be appropriately added to the second elastic material.

Examples of the conductive fibrous filler include carbon fibers, zinc white, metal fibers such as aluminum fibers, and metal compound fibers such as ferrite (MO.Fe ₂ O) fibers.

The first elastic material used for the base material and the second elastic material used for the electromagnetic wave shield coating member are preferably the same elastic material. By using the same kind of elastic material, it is possible to ensure the adhesion between the base material and the electromagnetic wave shield covering member.

The shape of the electromagnetic wave shielding gasket can be an appropriate shape according to the shape of the gap. For example, the cross-sectional shape can be various shapes such as an elliptical shape and a rectangular shape.

Manufacturing Method, etc. The base material and the electromagnetic wave shield covering member can be molded by an appropriate method such as extrusion molding or molding. It is possible to disperse the conductive fibrous filler of the electromagnetic wave shield covering member in the second elastic material and orient it in a certain direction by a known orientation control method. This orientation control method is
This is a method that utilizes the phenomenon that the molecules are arranged (orientated) along the direction in which the material flows or the directional filler in the material is arranged (orientated). For example, injection using a mold When molding a product by molding, transfer molding, etc., the molecular arrangement (orientation) of the material depends on the position or length of the gate (gate) through which the material is poured into the mold.
Alternatively, the arrangement (orientation) of the filler can be set.

The molded base material and the electromagnetic wave shield covering member can be bonded together by an appropriate method. When both crosslinked rubber is used as the first elastic material and the second elastic material, the base material and the electromagnetic wave shield covering member can be adhered by vulcanization molding at the same time when molding by a molding method. That is, a crosslinked rubber is used as both the first elastic material and the second elastic material, and when the crosslinked rubber is in an uncrosslinked state, the surface serving as the blocking surface of the base material and the electromagnetic wave shield coating member are adhered to each other at the same time. Sulfur molding is preferred. By doing so, the crosslinked rubber is crosslinked across the contact surface between the first elastic material and the second elastic material, and the base material and the electromagnetic wave shield covering member can be firmly bonded. Even in this case, stronger adhesion can be obtained by using the same type of cross-linked rubber for the first elastic material and the second elastic material.

Further, it is possible to bond the first elastic material and the second elastic material using an appropriate adhesive in consideration of the materials.

Mode of Use The electromagnetic wave shielding gasket of the present invention is used in a gap between two electromagnetic wave shielding case members used in an electromagnetic wave shielding case. By being used for the gap in this way, the gap between the two electromagnetic wave shielding case members can be sealed to ensure watertightness and airtightness, and also to prevent electromagnetic waves from passing through the gap. it can.

The electromagnetic wave shielding case in which the electromagnetic wave shielding gasket of the present invention is used is the electromagnetic wave shielding case of the second invention. Therefore, a further description of the usage of the electromagnetic wave shielding gasket will be given in the description of the electromagnetic wave shielding case of the second invention.

(Second invention: electromagnetic wave shielding case)
The electromagnetic wave shielding case of the second invention is at least 2
One electromagnetic wave shielding case member and an electromagnetic wave shielding case member that are interposed between the two electromagnetic wave shielding case members to seal the gap between the two electromagnetic wave shielding case members and to shield electromagnetic waves from passing through the gap. This electromagnetic wave shielding gasket is the electromagnetic wave shielding gasket of the first invention.

At least two cases are provided for the electromagnetic wave shield.
One electromagnetic wave shielding case member and the electromagnetic wave shielding gasket of the first invention interposed between these electromagnetic wave shielding case members. The electromagnetic wave shielding gasket of the first invention is as described above.

The electromagnetic wave shielding case member is a member that constitutes an electromagnetic wave shielding case that houses an electronic circuit. This electromagnetic wave shielding case member is generally formed of a conductive material such as a press-formed product of an iron plate or an aluminum die cast product, and has electromagnetic wave shielding performance.

Examples of the electromagnetic wave shielding case member include a body of the electromagnetic wave shielding case having a lid and an opening closed by the lid. A groove for inserting the electromagnetic wave shielding gasket is formed on one side of the two electromagnetic wave shielding case members, and the electromagnetic wave shielding gasket is pressed against the other side of the electromagnetic wave shielding case member. You can In any case, the electromagnetic shield gasket is 2
The gap between two electromagnetic wave shielding case members is blocked to ensure airtightness and watertightness, and also to shield electromagnetic waves.

The electromagnetic wave shielding case of the present invention is
It is only necessary to have at least two electromagnetic wave shielding case members, and it is also possible to have three or more electromagnetic wave shielding case members. In this case, the electromagnetic wave shielding case member in which the electromagnetic wave shielding gasket of the first invention can be used in each gap of the electromagnetic wave shielding case member can be manufactured by an appropriate method. Also the first
The method for manufacturing the gasket for electromagnetic wave shielding of the invention is as described above.

The electromagnetic wave shielding case can be manufactured by using these electromagnetic wave shielding case members, electromagnetic wave shielding gaskets and necessary members.

By using this electromagnetic wave shielding case, the electronic circuit housed therein can be protected from water and other liquids and dust in the air, and can also shield electromagnetic waves. Further, since the electromagnetic wave shielding gasket can be miniaturized, the electromagnetic wave shielding case can have various shapes, and the degree of freedom in design is increased.

(Examples) Examples of the gasket for electromagnetic wave shielding of the present invention will be specifically described below. The electromagnetic wave shielding gasket of the example is shown in FIG. The electromagnetic wave shielding gasket of this embodiment is supposed to be used in an environment in which a liquid such as air dust, water, and a brake fluid containing glycol ether as a main component is present. FIG. 1 is a sectional view of an electromagnetic wave shielding gasket of an embodiment in a used state.

The gasket 30 for electromagnetic wave shielding of the embodiment is composed of a base material 31.
And an electromagnetic wave shield covering member 32 covering one of the shielding surfaces of the base material 31. Here, the composition of the base material 31 and the electromagnetic wave shield coating member 32 is shown in Table 1.
Shown in. The base material 31 and the electromagnetic wave shield covering member 32
The constituent elements of the above are not shown except for the carbon fiber 32a.

[0044]

[Table 1]

An ethylene propylene copolymer rubber (hereinafter appropriately abbreviated as "EPDM rubber") was used as the first elastic material which is the main body of the base material 31. In addition, the electromagnetic wave shield covering member 3
EPDM rubber was similarly used for the second elastic material used in No. 2. EPDM rubber has good resistance to brake fluid mainly composed of glycol ether and water.

The base material 31 is composed of EPDM rubber, carbon black, and zinc oxide (ZnO) as a main component and an inorganic material. The EPDM rubber, which is the first elastic material, is 56 mass% based on the mass of the entire base material as 100 mass%, and contains 3.7 mass% of sulfur. The carbon black used as a reinforcing material is 43% by mass, and the inorganic substance is 1%.
Mass% is included.

The electromagnetic wave shield coating member 32 is composed of EPDM rubber, carbon black, carbon fibers 32a, and zinc oxide (ZnO) as the main component and an inorganic substance. The second elastic material, EPDM rubber, has a mass of the entire base material of 1
It is 65% by mass as 00% by mass, and contains 3.2% by mass of sulfur. The carbon black used as a reinforcing material is contained in an amount of 27% by mass, and the carbon fiber is a conductive fibrous filler in an amount of 15% by mass. Further, the inorganic substance is contained in an amount of 3% by mass. The carbon fibers 32a are oriented and dispersed in the direction connecting the first case member 10 and the second case member 20, that is, in the vertical direction in FIG.

The electromagnetic wave shield coating member 32 is coated on the left side of the substrate 10 in FIG. This base material 31
The EPDM rubber and the electromagnetic wave shield covering member used for the base material 31 are adhered to each other by contacting the base material 31 and the electromagnetic wave shield covering member 32 before the EPDM rubbers are crosslinked. The EPDM rubber used for No. 32 was simultaneously vulcanized and bonded to bond. By vulcanization and molding in such a contact state, cross-linking occurs across the contact surface between the base material 31 and the electromagnetic wave shield covering member 32, and the base material 31 and the electromagnetic wave shield covering member 32.
The bond with and becomes strong.

Usage Mode The electromagnetic wave shielding gasket 30 of the embodiment is used in the gap between the first case member 10 and the socket-shaped second case member 20. Both the first case member 10 and the second case member 20 are made of a conductive material and are electromagnetic wave shielding case members.

One end of the electromagnetic wave shielding gasket 30 of this embodiment is pressed against the end face of the first case member 10. Then, it is inserted into the socket-shaped second case member 20. In this manner, the electromagnetic wave shielding gasket 30 has one end pressed against the first case member 10 and the other end inserted into the socket-shaped second case member 20, whereby the first case member 10 and the second case member 20 are separated from each other. The airtightness and watertightness in this gap are secured by blocking and sealing the gap.
Further, the EP used for the electromagnetic wave shielding gasket 30
As described above, the DM rubber has excellent resistance to brake fluid mainly containing glycol ether and the like, and water, so that it can be used for a long time even when used in an environment where such brake fluid and water are present. it can.

Further, the electromagnetic wave shield covering member 32 of the electromagnetic wave shield gasket 30 includes the first case member 10 and the second case member.
Since the gap with the case member is blocked, it is possible to block passage of electromagnetic waves through this gap. Further, the carbon fibers 32a dispersed in the electromagnetic wave shield covering member 32 can effectively shield the electromagnetic waves that try to pass through the gap between the first case member 10 and the second case member 20.

In this embodiment, from the positional relationship between the first case member 10 and the second case member 20 which are conductors,
In FIG. 1, electromagnetic waves whose vibration direction is vertical are originally restricted from passing, and electromagnetic waves whose vibration direction is horizontal can pass through this gap. However, since the carbon fibers 32a are oriented vertically in this gap, the electromagnetic waves whose vibration direction is horizontal are blocked by the carbon fibers 32a.

Since the electromagnetic wave shield covering member 32 is in contact with the first case member 10 and the second case member 20, the electromagnetic wave shielding performance can be ensured.

(Measurement Test) The following measurement test was performed using the composition used for the base material 31 of the gasket 30 for electromagnetic wave shielding and the composition used for the electromagnetic wave shield coating member 32 of the above-described examples. In the following measurement test,
The composition used for the base material 31 is called general rubber, and the composition used for the electromagnetic wave shield covering member is called electromagnetic wave shield rubber. That is, the compositions of the general rubber and the electromagnetic wave shielding rubber are the compositions described in Table 1 above.

Hardness etc. The hardness (Hs), tensile breaking strength (MPa), tensile breaking elongation (%) and compression set (%) of the general rubber and the electromagnetic wave shielding rubber were measured. The measurement results are shown in Table 2.

[0056]

[Table 2]

The hardness, tensile strength at break, and tensile elongation at break were measured according to JIS K6253 and 6251. Regarding compression set, JIS
Performed by the measuring method specified in K6262, and at 100 ° C for 7
The data was measured after 0 hours.

The following can be seen from these measurement results. General rubber has hardness, tensile breaking strength, tensile breaking elongation,
Good results have been obtained regarding compression set and the like. Therefore, general rubber has good elasticity and is excellent in ensuring airtightness and watertightness. Further, it is excellent in compression set, which is an important characteristic for ensuring watertightness and liquidtightness. Therefore, it can be seen that general rubber is a material excellent in ensuring airtightness and watertightness.

On the other hand, it is understood that the electromagnetic wave shielding rubber in which carbon fibers are dispersed is harder and has a lower elasticity as compared with general rubber. Therefore, it is difficult to secure the watertightness and airtightness only with the electromagnetic wave shielding rubber. In particular, since the compression set, which is an important property for ensuring watertightness and liquidtightness, is inferior, airtightness and watertightness cannot be satisfactorily achieved by the electromagnetic wave shielding rubber alone.

Electromagnetic Wave Shielding Performance Using an Shielding Performance Tester manufactured by Advantest Co., a measurement test of the electric field shielding performance and the magnetic field shielding performance was performed on the electromagnetic wave shielding rubber and the general rubber by the transmission attenuation measuring method.

In the measurement test of the electric field shield performance and the magnetic field shield performance, a plate-shaped electromagnetic wave shield rubber and general rubber were used as test pieces. Then, in a anechoic chamber, as schematically shown in FIG. 2, in a state in which a plate-shaped sample TP is erected vertically between a transmission antenna SA and a reception antenna RA, which are installed at a distance of 1 cm, Radio waves are transmitted from the transmitting antenna SA to the receiving antenna RA,
The electric field shielding performance and the magnetic field shielding performance of the plate-shaped sample TP were measured.

The carbon fibers dispersed in the electromagnetic wave shielding rubber had a fiber length of about 140 to 200 μm and a fiber diameter of about 7 μm.

As a first measurement test, a specimen of electromagnetic wave shielding rubber having a thickness of 4 mm, a thickness of 3 mm, a thickness of 2 mm and a thickness of 0.5 mm and a specimen of a general rubber having a thickness of 2 mm were prepared. The electric field shielding performance and the magnetic field shielding performance of the test piece were measured by the above transmission attenuation measurement method.

In this measurement test, with respect to the sample of the electromagnetic wave shielding rubber, the carbon fibers dispersed in the electromagnetic wave shielding rubber were applied in both the traveling direction and the amplitude direction of the electric wave transmitted from the transmitting antenna to the receiving antenna. On the other hand, it was arranged to be vertically oriented.

The measurement results of this first measurement test are shown in FIGS. 3 and 4. The electric field shielding performance is shown in FIG.
Shows the magnetic field shield performance.

From the measurement results shown in FIG. 3, it can be seen that the electromagnetic wave shielding rubber sample is superior in electric field shielding performance to the general rubber sample. More specifically, general rubber exhibits a slight electric field shielding performance in the frequency band of 450 MHz or less, and has almost no electric field shielding performance in the frequency band of more than 450 MHz. On the other hand, the electromagnetic wave shielding rubber shows good electric field shielding performance even in the frequency band of 100 to 1000 MHz. It can also be seen that the thickness dependence is large.

Further, from the measurement results shown in FIG. 4, the electromagnetic wave shielding rubber is superior to the general rubber also in the magnetic field shielding performance. It is also understood that the electromagnetic wave shielding rubber has a large thickness dependency.

Therefore, it is understood that, when forming the gasket for electromagnetic wave shielding, it is not possible to obtain the electromagnetic wave shielding performance only with the general rubber, and it is necessary to use the electromagnetic wave shielding rubber in order to obtain the electromagnetic wave shielding performance.

As a second measurement test, the electric field shielding performance of a sample of electromagnetic wave shielding rubber having a thickness of 4 mm was measured by the above transmission attenuation measuring method. In this measurement test, with respect to the amplitude direction of the electromagnetic wave used in the measurement test, the case where the direction of the orientation of the carbon fiber was made vertical and the direction of the direction of the carbon fiber of the sample of the electromagnetic wave shielding rubber having a thickness of 4 mm was measured.
In both cases, the direction of orientation of the carbon fibers is perpendicular to the traveling direction of the electromagnetic wave. The results of this second measurement test are shown in FIG.

Further, as a third measurement test, a sample having a thickness of 4 mm, a sample having a thickness of 3 mm and a sample having a thickness of 2
A test piece having a thickness of 0.5 mm and a test piece having a thickness of 0.5 mm were prepared. Then, for each of these electromagnetic wave shielding rubber specimens, the numerical value at which the electric field shielding performance is maximized when the carbon fiber is oriented perpendicular to the amplitude direction of the electromagnetic wave and in the case where the carbon fiber is oriented parallel to the electromagnetic wave amplitude direction is the above-mentioned transmission attenuation measurement. It was measured by the method. For the traveling direction of electromagnetic waves in this case,
The direction of carbon fiber orientation is vertical. The measurement result is shown in FIG.

From the measurement results shown in FIGS. 5 and 6, it can be seen that the electric field shielding performance is better when the carbon fibers are oriented perpendicularly to the amplitude direction of the electromagnetic wave than when they are oriented parallel. . Therefore, the electric field shielding performance can be improved by using the electromagnetic wave shielding rubber so that the orientation direction of the carbon fibers is perpendicular to both the traveling direction and the amplitude direction of the electromagnetic wave. Therefore, if the same electric field shielding performance is to be obtained, the electromagnetic shielding rubber may be thinner when the carbon fibers are oriented perpendicularly to the amplitude direction of the electromagnetic waves.

For example, from FIG. 6, when a numerical value of 30 dB is required for the maximum electric field shielding performance, and the carbon fiber is oriented perpendicular to the amplitude direction of the electromagnetic wave, a thickness of about 0.5 mm may be used. However, if the carbon fiber is oriented parallel to the amplitude direction of the electromagnetic wave, 2 mm
It needs a certain thickness. Therefore, when the orientation direction of the carbon fibers is perpendicular to the amplitude direction, the thickness may be about one-fourth that of the parallel direction.

Therefore, in consideration of the traveling direction and the amplitude direction of the electromagnetic wave that is going to pass through the place where the electromagnetic wave shielding rubber is used, if the orientation direction of the carbon fiber is set to be perpendicular to both of them, a good electric field shield is obtained. It turns out that the performance can be obtained.

The fact that the orientation direction of the carbon fiber is perpendicular to both the traveling direction and the amplitude direction of the electromagnetic wave means that when the electromagnetic wave shielding gasket is used in the gap between the two electromagnetic wave shielding case members. That is, the carbon fibers dispersed in the shield covering member are oriented in the direction connecting the two electromagnetic wave shielding case members.

As a result, the thickness of the electromagnetic wave shield rubber can be reduced, the electromagnetic wave shield gasket can be miniaturized, and the degree of freedom in design is increased.

Adhesion Further, the adhesion between the electromagnetic wave shielding rubber and the general rubber was measured. First, as shown in FIG. 7, width 3 of the stage before cross-linking
Width 30 as same as 0mm rectangular electromagnetic wave shield rubber A
It was arranged in series so as to partially overlap the rectangular general rubber B of mm. The length of the portion C where the electromagnetic wave shielding rubber A and the general rubber B overlap is 30 mm, and the length of the electromagnetic wave shielding rubber A and the general rubber B which are partially overlapped and arranged in series is 150 mm.

In this state, vulcanization molding was carried out at the same time, and crosslinking was caused so as to straddle the contact surface between the electromagnetic wave shielding rubber A and the general rubber B. As a result, the electromagnetic wave shielding rubber A and the general rubber B were adhered to each other over a length of 30 mm to obtain a molded body having a length of 150 mm and a width of 30 mm.

A tensile test was performed on this molded product by the method specified in JIS K6251. As a result, the portion C where the electromagnetic wave shielding rubber A and the general rubber B overlap did not dissociate at the contact surface, and the molded body itself broke.

From here, the base material and the electromagnetic wave shield member are brought into contact with each other before the cross-linked rubbers used as the first elastic material and the second elastic material are cross-linked, and are simultaneously vulcanized and molded so as to straddle the contact surfaces. It can be seen that the base material and the electromagnetic wave shield member can be firmly bonded by crosslinking.
Therefore, it is understood that the watertightness and the airtightness are not impaired by the peeling of the base material and the electromagnetic wave shield member.

[0080]

EFFECT OF THE INVENTION The electromagnetic wave shielding gasket of the present invention can be miniaturized and have good electromagnetic wave shielding performance. That is, even if the electromagnetic wave shield covering member is made thin, good electromagnetic wave shield performance can be maintained, so that the electromagnetic wave shield gasket can be miniaturized.

In the electromagnetic wave shield gasket of the present invention, the first elastic material used for the base material and the second elastic material used for the electromagnetic wave shield covering member are made of the same kind of crosslinked rubber, and are vulcanized and molded in a superposed state. The base material and the electromagnetic wave shield covering member can be firmly adhered to each other.

The electromagnetic wave shielding case of the present invention can be formed into various shapes by using the electromagnetic wave shielding gasket which can be downsized and can obtain good electromagnetic wave shielding performance, and thus the design freedom can be obtained. You can do it.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an electromagnetic shield gasket of an example in a used state.

FIG. 2 is a diagram schematically showing a positional relationship between a sample, a transmitting antenna, and a receiving antenna used in a transmission attenuation measuring method.

FIG. 3 is a graph showing the electric field shielding performance of each test piece obtained in the first measurement test.

FIG. 4 is a graph showing the magnetic field shield performance of each test piece obtained in the first measurement test.

FIG. 5 is a graph showing the electric field shield performance obtained in the second measurement test.

FIG. 6 is a graph showing the maximum electric field shield performance obtained in the third measurement test.

FIG. 7 is a diagram showing a state in which a general rubber used in an adhesion test and an electromagnetic wave shielding rubber are overlapped and adhered.

[Explanation of symbols]

10: 1st case member 20: 2nd case member 30: Electromagnetic wave shield gasket 31: Base material 32: Electromagnetic wave shield covering member 32a: Carbon fiber TP: Specimen SA: Transmission antenna RA: Reception antenna A: Electromagnetic wave shield rubber B : General rubber C: Part where electromagnetic wave shielding rubber and general rubber overlap

Claims (8)

[Claims] 1. An electromagnetic wave shielding gasket that is interposed between two electromagnetic wave shielding case members to seal a gap between the two electromagnetic wave shielding case members and to prevent electromagnetic waves from passing through the gap. 1. A base material mainly composed of an elastic material, which seals by blocking the gap, a second elastic material, and a conductive fibrous material dispersed in the second elastic material and oriented in a direction connecting the two electromagnetic wave shielding case members. An electromagnetic wave shielding gasket, comprising: a filler, and at least one shielding surface that shields the gap of the base material. 2. The gasket for electromagnetic wave shielding according to claim 1, wherein the conductive fibrous filler is at least one kind selected from carbon fiber, zinc white, and metal fiber. 3. The electromagnetic wave shielding gasket according to claim 1, wherein both the first elastic material and the second elastic material are crosslinked rubber. 4. The first elastic material and the second elastic material are the same type of cross-linked rubber, and the base material and the electromagnetic wave shield covering member are adhered by being vulcanized and molded in a superposed state. The gasket for electromagnetic wave shielding according to claim 3, which is provided. 5. An electromagnetic wave passing through the gap by interposing at least two electromagnetic wave shielding case members and two electromagnetic wave shielding case members interposed therebetween. In a case for an electromagnetic wave shield having a gasket for shielding an electromagnetic wave, the gasket for an electromagnetic wave shield is mainly composed of a first elastic material, a base material for blocking and sealing the gap, a second elastic material and the second elastic material. (2) An electromagnetic wave which is dispersed in an elastic material and includes a conductive fibrous filler oriented in a direction connecting the two electromagnetic wave shielding case members, the electromagnetic wave being covered by at least one shielding surface which blocks the gap of the base material. An electromagnetic wave shield case comprising a shield covering member. 6. The electromagnetic wave shielding case according to claim 5, wherein the conductive fibrous filler is at least one selected from carbon fiber, zinc white, and metal fiber. 7. The electromagnetic wave shielding case according to claim 5, wherein each of the first elastic material and the second elastic material is a crosslinked rubber. 8. The first elastic material and the second elastic material are the same type of crosslinked rubber, and the base material and the electromagnetic wave shield covering member are bonded by being vulcanized and molded in a state of being superposed on each other. The electromagnetic wave shielding case according to claim 7.