JP2002111270A - Electromagnetic wave shielding gasket - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic wave shielding gasket which is used for shielding a gap of a conductive case from electromagnetic waves and capable of preventing the deformation of the case due to external forces. SOLUTION: A conductive cloth 20 is folded back with the ends joined at a central portion and both sides of the folded cloth is further folded back to form compressed parts 12, thus forming a conductive block 10. The conductive cloth 20 is used to suppress the compression ratio of the conductive block 10 due to external forces, and the compressed parts 12 are provided for displaying a sufficient electromagnetic wave shield effect without increasing the ground resistance even with a low compression ratio. In a recess 11, an adhesive part 30 of an adhesive layer 32 laminated on sponge 31 is provided for fixing the gasket to the conductive case.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gasket for shielding electromagnetic waves, and more particularly, to a gasket for shielding electromagnetic waves, which is disposed in a gap between conductive cases and shields an electromagnetic wave passing through the gap.

[0002]

2. Description of the Related Art Conventionally, there has been known an electromagnetic shielding gasket which is disposed in a gap between conductive cases and shields an electromagnetic wave which is going to pass through the gap. In particular, in recent years, with the development of computer technology, many devices incorporating a microcomputer have been commercialized, and in such electronic devices, the technology of shielding electromagnetic waves has become indispensable.

[0003] Such an electromagnetic wave shielding gasket is provided for the purpose of closely adhering to the gap between the conductive cases.
It was common to ensure sufficient elasticity.

[0004]

However, considering a portable telephone as an example of a small device in which such a gasket for shielding electromagnetic waves is provided, the gasket has sufficient elasticity as in the prior art. The following inconveniences occur.

[0005] That is, the body case of the portable telephone is deformed by an external force. More specifically, looking at the cross section of the main body case having conductivity as shown in FIG. 5, the upper part and the lower part have a box-like structure to increase the overall rigidity. However, when a highly flexible gasket is interposed in the gap between the upper part and the lower part, the gasket is partially compressed by the load applied to the main body case, or the gap between the edges of the main body case is displaced. And the entire body case is deformed to be twisted. That is, if the flexibility of the gasket is too high, the rigidity of the main body case is reduced.

When the mobile phone is deformed, such as by twisting the main body case, the ground member mounted on the printed wiring board may be separated from the ground plane. In such a case, the call is interrupted depending on the specifications of the mobile phone. Further, noise in the audible range may be generated, and the call may be disturbed.

[0007] A problem similar to this occurs not only in portable telephones. The present invention has been made in order to solve such a problem, and is used for a conductive case such as a main body case to shield electromagnetic waves, and can prevent deformation of the conductive case due to external force. An object of the present invention is to provide a gasket for shielding electromagnetic waves.

[0008]

According to the first aspect of the present invention, there is provided a gasket for shielding electromagnetic waves, comprising: a gap between an upper member and a lower member constituting a conductive case; And shields electromagnetic waves passing through the gap.

In the present invention, the conductive portion compressed by the upper member and the lower member is formed by bending a conductive cloth or metal foil. The “conductive cloth” referred to here is made of a thin metal wire (monel, copper weld, aluminum, tin-plated copper, etc.) or a metal-coated fiber (fiber coated with metal by means of plating, vapor deposition, sputtering, or the like on a synthetic fiber). It is conceivable to use a conductive woven fabric in which a multifilament yarn or a monofilament yarn is woven. In addition, a nonwoven fabric may be used as long as it has conductivity. On the other hand, the “metal foil” includes a metal foil provided with a synthetic resin film layer on the back surface. As the metal foil, it is usually considered that an aluminum foil is used.

By pressing at least one end of the conductive portion in a predetermined direction, a press-contact portion for mainly conducting the above-mentioned two members is formed. Since it is at least one end, there is a case where a press contact portion is formed only on one side in a predetermined direction and a case where press contact portions are formed on both sides.

The present applicant has paid attention to the fact that when the compression ratio of the gasket exceeds 10%, a conductive case such as a main body case is deformed by an external force, and a problem is likely to occur. For example, even if a mobile phone is taken as an example, when the compression ratio of the gasket becomes 10% or more, the amount of deformation such as torsion of the main body case increases, and a good grounding state between the printed circuit board and the main body case by the ground member is obtained. There is a high possibility that the call will be interrupted and interrupted, or noise in the audible range will occur. Therefore, a gasket that can obtain a sufficient electromagnetic wave shielding effect at a compression ratio of less than 10% is required.

According to the present invention, since the conductive portion is formed of a conductive material such as a conductive cloth or a metal foil which is relatively difficult to deform even when compressed, it is highly possible that the compression ratio can be suppressed to less than 10%. The deformation of the main body case can be prevented. And since the press contact part was formed by bending the end of the conductive part, even if the compression ratio was small,
The ground resistance can be reduced, and sufficient conduction between the upper member and the lower member can be achieved.

Therefore, as shown in FIG. 5, if this gasket is applied to a main body case composed of an upper portion and a lower portion, a sufficient electromagnetic wave shielding effect can be obtained, and the upper portion and the lower portion can be connected to each other. The displacement caused by the external force is reduced, and the deformation of the main body case due to the external force can be suppressed. That is, by suppressing the amount of deformation of the gasket, the rigidity of the conductive case can be increased. Preferably, the compression ratio is less than 5% in a state where the compression ratio is set in the gap between the conductive cases.

It is conceivable that the pressure contact portion is formed to be thicker than other portions, for example, by folding a conductive cloth or a metal foil in a double or triple manner. However, since it is sufficient that sufficient electrical conduction is ensured by the press contact portion, the end portion may be slightly bent so as to be inclined, and this portion may be used as a compression portion.

By the way, the above-mentioned conductive portion may be formed by bending only a conductive cloth or a metal foil, but in consideration of the case where the end portion of the conductive portion is slightly bent as described above. As shown in (1), it is preferable that the conductive portion includes a shape maintaining layer as a core material for maintaining the shape. As the core material, a material that can reduce the compression ratio due to an external force to less than 10% and can maintain the shape of the conductive portion is used. For example, a plastic material is used. At this time, it is conceivable that the shape maintaining layer is provided so as to be sandwiched between the inner surfaces of the folded conductive cloth. At this time, the outer surface of the conductive cloth or metal foil comes into contact with both members. For example, a shape maintaining layer may be provided on an inner portion of a folded conductive cloth or metal foil. A conductive cloth or a metal foil usually has a front surface and a back surface. For example, when the conductive cloth is a woven cloth, the above-mentioned multifilament yarn or monofilament yarn may be broken during weaving, and in this case, the cut yarn is tied on the back surface. Therefore, in order to obtain stable contact, it is desirable to use the surface of the conductive cloth. That is, if the conductive cloth or the metal foil is folded back and the shape maintaining layer is sandwiched between the back surfaces, the surface becomes the contact surface, so that more stable conduction is achieved.

From the viewpoint of maintaining the shape of the bent press-contact portion, it is conceivable that the shape maintaining layer is made of a material that melts when heat is applied. At this time, the pressure contact portion is formed in a state where the shape maintaining layer is melted. For example, a shape maintaining layer is provided by applying a hot melt to an inner part of the folded conductive cloth and sandwiching a melt tape. Then, heat is applied by an iron or the like to bend the conductive cloth into a predetermined shape to form a press-contact portion. In this case, even when the conductive cloth or the metal foil is used, the press-contact portion can be easily formed and the shape can be maintained.

If the gasket is formed to be elongated in a direction perpendicular to the predetermined direction as described above, the gasket can be cut to an appropriate length depending on the place of use and can be used conveniently. It is. In the case where the present gasket is used for a groove formed in the conductive case or the like, the gasket does not need to have an adhesive property. On the other hand, in a case where the present gasket is sandwiched between flat surfaces, it is conceivable to adopt the configuration described in claim 7. That is, it further includes an adhesive portion having adhesiveness. The adhesive portion may be realized by a double-sided tape or the like. At this time, as described in claim 8, when the conductive portion is compressed by both members, it is preferable that the conductive portion bends in the compression direction by a load acting on the adhesive portion, and the press-contact portion be pressed against the conductive case. In this way, the electromagnetic wave shielding effect is outstanding.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing a gasket 1 as an “electromagnetic wave shielding gasket” of an embodiment.

The gasket 1 comprises a conductive part 10 and an adhesive part 30.
And The gasket 1 is formed as a long member that is long in the longitudinal direction (the direction indicated by the symbol A), is cut into a length of, for example, 1 m, is transported, and further has a length of, for example, 50 mm in accordance with a place of use. It is supplied after being cut to a suitable length. The short direction (the direction indicated by the symbol B) is formed to have a predetermined width of, for example, 3 mm.

The conductive portion 10 is formed by folding a conductive cloth 20. The conductive cloth 20 is a conductive woven cloth in which a multifilament yarn or a monofilament yarn made of, for example, a thin metal wire or a metal-coated fiber is woven. The thickness of the conductive cloth 20 is 1 mm or less, preferably 0.7 mm or less in order to reduce the compression ratio.

The conductive portion 10 is formed by bending the conductive cloth 20 as follows. First, as shown in FIG. 2A, the conductive cloth 20 is folded back so that its ends 21 meet at the center. Note that a hot melt is applied to the inner surface of the conductive cloth 20 folded in this way. Then, heat is applied to the conductive cloth 20 in this state with an iron or the like,
The hot melt is melted, and as shown in FIG. 2B, the side portions 22 are further turned back to form the press contact portions 12. In the press contact portion 12, the conductive cloth 20 is quadruple, so that it is thicker than the central portion, and the concave portion 11 is formed in the central portion. When the molten hot melt solidifies, the conductive cloth 20
Will maintain the shape shown in FIG. 2 (b). Therefore, this hot melt corresponds to a “shape maintaining layer”. In this example, hot melt was applied.
It is also conceivable to use a melt tape.

The above-mentioned adhesive portion 30 is provided in the above-mentioned concave portion 11.
Has been fixed. The adhesive portion 30 is a long member along the concave portion 11, and is formed by laminating an adhesive layer 32 on a thin sponge 31 as shown in FIG. 1. With this adhesive layer 32, the gasket 1 is attached to a predetermined position of the conductive case.

In this embodiment, since the conductive portion 10 is formed by bending the conductive cloth 20 which is not easily deformed even when compressed, it is interposed in the gap between the upper portion and the lower portion of the main body case as shown in FIG. Then, the amount of deformation of the gasket 1 is reduced, so that the displacement between the upper part and the lower part of the main body case is reduced, and the rigidity of the main body case is increased. Thereby, deformation of the main body case due to external force can be suppressed.

Specifically, for example, a length of 50 mm and a width of 3 m
As shown in Fig. 6 (b), a 10% compression of this gasket required a relatively large compression force of about 10 to 20N, and further increased the compression force as shown in Fig. 6 (b). As a result, the required load increased rapidly.

Therefore, for example, if the gasket 1 of this embodiment is employed in a main body case of a portable telephone, even if an external force acts, a good grounding state by the grounding member can be maintained, and the telephone conversation is interrupted. Possibility can be reduced. Further, generation of audible noise can be prevented.

Further, in the gasket 1 of this embodiment, since the adhesive portion 30 is provided in the concave portion 11 which is the central portion of the conductive portion 10, the fixing work of the gasket 1 becomes easy, which is convenient for the operator. . Furthermore, in the gasket 1 of the present embodiment, since the press-contact portions 12 are formed by folding the both sides 22 of the conductive cloth 20, the press-contact portions 12 are pressed against the main body case, and even if the amount of deformation of the conductive portions 10 is small, the ground contact is made. Resistance can be reduced, and reliable conduction can be achieved. That is, a sufficient electromagnetic wave shielding effect can be obtained.

Specifically, when a test was performed using the gasket of the above sample, as shown in FIG. 6A, when the gasket was formed without folding back the end, a compression ratio of 10% and 5Ω or more were obtained. While the ground resistance is generated, the end is turned back as described above, and the conduction is mainly conducted at this end. As a result, even if the compression ratio is 10% or less, the resistance value is suppressed to about 0.1Ω or less. Was.

Further, in the gasket 1 of this embodiment, since the conductive portion 10 is formed in a long shape, it is easy to manufacture, and can be cut into an appropriate length for use.
It can be placed in various places. Furthermore, in the gasket 1 of the present embodiment, hot melt is applied to the inner surface of the conductive cloth 20, and the outer surface is brought into contact with the main body case. In other words, the conductive cloth 20 generally has a surface suitable as a contact surface and a back surface which is not so, but in the configuration as in the present embodiment, one surface of the conductive cloth 20, that is, a contact surface is suitable. The contact with the main body case can be realized using the bent surface.

Then, after applying heat with an iron or the like to melt the hot melt in the state shown in FIG.
As shown in FIG. 2B, the press contact portions 12 were formed by folding the both side portions 22. Therefore, after the hot melt is solidified, the shape of the press contact portion 12 is maintained.

As described above, the present invention is not limited to such an embodiment at all, and can be implemented in various forms without departing from the gist of the present invention. (A) For example, in the above embodiment, as shown in FIGS. 2A and 2B, the conductive portion 10 is folded back so that the ends 21 of the conductive cloth 20 meet at the center (FIG. 2A). (See FIG. 2B), and the press-contact portion 12 is formed by completely folding the both side portions 22 in this folded state (see FIG. 2B). However, as long as sufficient conduction is achieved, the pressing portion may be formed in any manner.

For example, like the conductive portion 40 shown in FIG. 3A, the side portions 22 of the conductive cloth 20 are folded back from the state shown in FIG.
2 may be formed. In this case, the side portions 22 are further bent inward, and the lower surface 40b is in close contact with the conductive case. Therefore, the both sides 22 are urged in the direction of the conductive case, and the adhesion of the press contact portion 42 is improved. The adhesive section 30 has the same configuration as in the above embodiment.

As shown in FIG. 3B, the end of the conductive cloth 20 is folded inward, and the leading end of the folded portion is further folded outward, as shown in FIG.
May be formed. In this case, the end 2 turned outward
1 will be in close contact with the conductive case,
In the press contact portion 52, the conductive cloth 20 is folded threefold.

(B) In the above embodiment, the shape of the conductive portion 10 is maintained by applying a hot melt to the inside of the conductive cloth 20. On the other hand, it is conceivable to form the conductive portion by winding the conductive cloth 20 around the core material. For example, FIG.
As shown in (c), it is conceivable to form the conductive portion 60 by using a plastic core material 81 having a U-shaped cross section and winding the conductive cloth 20 so as to cover the outer periphery of the core material 81. In this case, since a concave portion is formed in the central portion in the short direction from the shape of the core material 81, it is conceivable to provide the adhesive portion 30 similar to that in the above embodiment in this concave portion.

As shown in FIG. 3 (d), for example, a plastic core material 82 having a rectangular cross section is used. The conductive portion 70 may be formed so as to cover the conductive portion 70. In this case, since the lower central portion is not covered with the conductive cloth 20, the adhesive portion 30 can be provided in this portion (recess).

In these examples, the core members 81 and 82 correspond to the “shape maintaining layers”, and the both ends of the conductive portions 60 and 70 are the press contact portions 62 and 72. By forming the conductive portions 60 and 70 using the cores 81 and 82 in this manner,
The conductive portions 60 and 70 formed in a long shape do not bend during the operation, which is convenient for the operator. Also,
When the gap between the conductive cases is relatively large, the conductive cloth 2
In order to form the conductive portion using the “0”, it is necessary to fold the conductive portion many times. However, when the core members 81 and 82 are used, the conductive portions 60 and 70 having the press contact portions 62 and 72 having a predetermined thickness can be easily manufactured. can do.

(C) If hot melt is applied to the inside of the conductive cloth 20 as in the above embodiment, both sides 22 of the conductive cloth 20 shown in FIG. 2A are further bent into various shapes. be able to. For example, as in a conductive portion 80 shown in FIG. 4A, it is conceivable to form the press contact portion 82 by bending both side portions 22 so as to curl. Further, as shown in FIG. 4B, it is conceivable to form the conductive portion 90 by slightly bending the both side portions 22 so as to be inclined to form the press contact portion 92.

By appropriately adjusting the width of the conductive portion 90 and the inclination of the press contact portion 92, the adhesive portion 30 is adhered to the lower portion of the main body case as shown in FIG. 4C. When the central portion of the conductive portion 90 is bent in the compression direction, that is, the central portion of the conductive portion 90 is moved downward by a load acting on the adhesive portion 30 from the lower portion, and the pressing portion 92 is moved downward. When you press against the side part,
Further, contact resistance can be reduced, and reliable conduction can be achieved. However, in this case, if the gap between the upper portion and the lower portion is further reduced, the upper surface of the conductive portion 90 eventually approaches a flat surface, and the effect of the adhesive portion 30 is reduced.

Therefore, as shown in FIG. 4D, it is conceivable to arrange the adhesive portion 30 on the upper surface side of the conductive portion 90. In this case, since the adhesive portion 30 is compressed by the load from the upper portion, the central portion of the conductive portion 90 is pushed down. In this case, even if the gap between the upper portion and the lower portion is further narrowed, the central portion will bend, and the press contact portion 92 will be urged downward, and as a result, the contact resistance may be reduced. As a result, reliable conduction can be achieved.

Incidentally, such a structure can also be adopted for the above-described conductive portions 10, 40, 50, and 80. In this case, it is conceivable to provide the adhesive portion 30 on the upper surface side of the conductive portions 10, 40, 50, and 80 as well as the conductive portion 90. (D) In the above embodiments, the conductive portions 10, 40, 50, 60, 70, 80, and 90 are formed by bending the conductive cloth 20, but a metal foil such as aluminum is used instead of the conductive cloth 20. You may. In that case, it is conceivable to provide a synthetic resin film layer or the like on the back surface of the metal foil to increase the strength.

(E) In the above embodiment, the conductive portion 1
The press contact portions 12, 42, 52, 62, 72, 82, 92 are formed at both end portions of 0, 40, 50, 60, 70, 80, 90, but one end portion of the conductive portion in a predetermined direction. It is also conceivable to form the pressure contact portion only on the contact portion. In this case, an adhesive portion may be provided at a portion other than the pressure contact portion, for example, at the other end or the center.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a gasket of an embodiment.

FIG. 2 is an explanatory diagram illustrating a structure of a conductive unit.

FIG. 3 is an explanatory diagram illustrating a schematic cross section of a gasket as another embodiment.

FIG. 4 is a schematic cross-sectional view of a gasket as another embodiment and an explanatory view exemplifying a state where a force in a compression direction acts on the gasket.

FIG. 5 is an explanatory diagram showing a relationship between a deformation occurring in a main body case and a gasket.

FIG. 6 is an explanatory diagram illustrating a relationship between a compression ratio and a resistance value and a relationship between a compression ratio and a compression force.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Gasket 10, 40, 50, 60, 70, 80, 90 ... Conductive part 10a ... Upper surface 10b, 40b, 50b ... Lower surface 11 ... Concave part 12, 42, 52, 62, 72, 82, 92 ... Pressure contact part 20 ... Conductive cloth 21 ... End 22 ... Both sides 30 ... Adhesive part 31 ... Sponge 32 ... Adhesive layer 81,82 ... Core material

Claims (8)

[Claims] 1. An electromagnetic wave shielding gasket disposed in a gap between an upper member and a lower member constituting a conductive case to shield electromagnetic waves passing through the gap, wherein the upper member and the lower member are provided. A conductive portion compressed with a member is formed of a conductive cloth or a metal foil, and at least one end of the conductive portion in a predetermined direction is bent to form a pressure contact portion for mainly conducting the two members. A gasket for electromagnetic wave shielding, characterized in that: 2. The gasket for an electromagnetic wave shield according to claim 1, wherein the pressure contact portion is formed to be thicker than other portions. 3. The gasket for an electromagnetic wave shield according to claim 1, wherein the conductive portion includes a shape maintaining layer as a core material for maintaining the shape. . 4. The gasket for electromagnetic wave shielding according to claim 3, wherein the shape maintaining layer is provided so as to be sandwiched between inner surfaces of a folded conductive cloth or a metal foil. A gasket for an electromagnetic wave shield, wherein an outer side surface of the gasket is in contact with the two members. 5. The gasket for an electromagnetic wave shield according to claim 3, wherein the shape maintaining layer is made of a material that melts when heat is applied, and the pressing portion is a state in which the shape maintaining layer is melted. A gasket for electromagnetic wave shielding, characterized by being formed of: 6. The electromagnetic wave shielding gasket according to claim 1, wherein said conductive portion is formed in an elongated shape in a direction perpendicular to said predetermined direction. Gasket for shielding. 7. The gasket for electromagnetic wave shielding according to claim 1, further comprising an adhesive portion having adhesiveness. 8. The gasket for an electromagnetic wave shield according to claim 7, wherein when the conductive portion is compressed by the two members, the conductive portion bends in a compression direction due to a load acting on the adhesive portion, and causes the press-contact portion to be electrically conductive. A gasket for electromagnetic wave shielding characterized by being pressed against a conductive case.