JPH06268391A - Electromagnetic shielding body and its manufacture - Google Patents

Abstract

PURPOSE:To produce an electromagnetic shielding body covering an opening with metal mesh in a single process. CONSTITUTION:An opening is covered with a metal mesh 3, and the portions other than said opening are made by embedding metal meshes continued to the metal mesh for the opening into the inside of a resin formed by reacted injection molding. An electromagnetic shielding body is formed by placing in advance the wire mesh 3 inside a cavity 12 of a pair of upper and lower metal molds 10 and 11 for reacted injection molding and, thereafter, pinching part of upper and lower surfaces of the metal mesh with a pair of resin-permiated shielding members 13 and 14 projected out oppositely from the upper and lower molds toward the cavity and creating polymerization reaction, under this condition, by injecting a reacting raw material liquid within the cavity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic wave shield and a method for producing the same, and more particularly, to an electromagnetic wave shield formed by molding a metal mesh or a porous metal plate and integrally molding the resin by a reaction injection molding method. The opening provided in the shield is covered with the metal mesh or the porous metal plate.

[0002]

2. Description of the Related Art Computer terminal equipment and AV equipment for OA equipment
The housing of an electronic device such as a device needs to be shielded to shield electromagnetic waves emitted from these electronic devices, and an opening needs to be provided for heat dissipation and wiring. These openings are preferably covered with a perforated metal plate such as a metal mesh or a punching metal having a heat dissipation void in order to prevent the leakage of electromagnetic waves at the heat dissipation opening and to prevent the entry of foreign matter. Even in the wiring openings, it is desirable that the portions other than the conductor penetrating portions be covered with a metal mesh or the like so that electromagnetic waves can be blocked and foreign matter can be prevented from entering.

Conventionally, as a method of applying an electromagnetic wave shield to a resin housing having an opening, a resin molded article having an opening is formed and then a conductive paint is sprayed or plated on its surface. A method for producing a resin molded product having an opening with a resin composition containing carbon, metal fibers, etc. (Japanese Patent Laid-Open No. 63-76500),
A method of molding a conductive woven fabric by molding it with a resin (Japanese Patent Laid-Open No. 61-152098, etc.) has been proposed.

[0004]

In the method described above, the conductive paint or plating on the surface is easily peeled off due to heat or with the passage of time, and there is a problem in the persistence of the electromagnetic wave shielding effect. In addition, there is also a problem in that a conductive coating is sprayed or a plating step is required after the resin molding, which results in two manufacturing steps. In the method described above, in order to obtain a good electromagnetic wave shielding effect, it is necessary to mix a large amount of fibers, molding is difficult, and it is difficult to obtain a product as designed.

Although the above method is the same as the above and the above methods, it is possible to form an electromagnetic wave shielding housing having an opening, but when it is desired to cover only the opening with a metal mesh, the opening is formed. It is necessary to attach a metal mesh to the part in the secondary process.

However, it is difficult to secure electrical contact with the electromagnetic wave shielding means (metal mesh or conductive woven cloth) provided on the housing itself, so that the metal mesh thus covering the opening is in contact with the electromagnetic wave shielding means. There is a drawback that electromagnetic waves leak from the part (gap). Further, when it is desired to cover only the opening with a metal mesh, a means for attaching the metal mesh needs to be provided on the housing side, and the metal mesh needs to be retrofitted, which requires a lot of work and increases the cost. There is a drawback. Furthermore, when the metal mesh is attached alone, there is a problem that rust is likely to occur.

Further, the housing of this type of electronic equipment requires strength, rigidity and impact resistance, but it has been difficult to satisfy the above-mentioned characteristics with a resin molded product. That is, in order to provide the above-mentioned characteristics, reinforcement with continuous fibers can be considered, but in conventional injection molding, the viscosity of the resin is high and molding becomes difficult. It is also possible to reinforce with a prepreg of continuous fibers, but most of the resins usable in this method are thermosetting resins, and there is a problem that a resin excellent in vibration absorption and impact resistance cannot be used. On the other hand, a method of combining a thermoplastic resin having excellent vibration absorption and impact resistance with continuous fibers and heating and then cooling may be considered, but 2
Since it needs to be heated to 50 ° C. or higher, there is a problem that it is difficult to arrange the fibers and it takes time to compress and heat.

The present invention has been made in view of the above problems, and has an opening in a part of a housing made of an electromagnetic wave shield, and the opening is covered with a porous metal plate such as a metal mesh or punching metal. It is an object of the present invention to be able to be integrally molded by reaction injection molding using a resin having strength, rigidity and impact resistance.

[0009]

In order to achieve the above object, the present invention provides a metal mesh or a perforated metal plate (hereinafter, only the metal mesh is described) in the cavities of a pair of upper and lower molds for reaction injection molding. The metal mesh is clamped in advance and then clamped, and the upper and lower surfaces of the metal mesh are partially clamped by a pair of resin permeation blocking materials that protrude from the upper and lower molds facing the cavity, and then inside the cavity. The unreacted raw material liquid is injected to cause a polymerization reaction, so that the part sandwiched by the resin permeation blocking material becomes an opening covered with a metal mesh, and the other part is the opening inside the resin. The present invention provides a method for manufacturing an electromagnetic wave shield in which a metal mesh continuous with the above metal mesh is embedded.

The pair of resin permeation blocking materials described above have a shape having an uneven surface that fits with the metal mesh on the surface, that is, a shape having a convex portion to be inserted into the void portion of the metal mesh and a concave portion corresponding to the metal wire. When the metal mesh is sandwiched and sandwiched, the protrusions come into pressure contact with each other to block the permeation of the resin, while the metal wire is sandwiched between the recesses and the permeation of the resin is allowed in the gap between the recess and the metal wire. Therefore, it is preferable that the metal wire of the metal mesh is thinly coated with resin. Thus, coating the metal mesh with the resin has an advantage that rust is less likely to occur. The pair of resin permeation barriers are formed of rubber having heat resistance.

Further, according to the present invention, a resin for injecting into the cavity is preliminarily arranged inside the cavity of the mold in a portion other than a portion to be an opening by the resin permeation blocking material. The present invention provides a method for producing an electromagnetic wave shielding material, which is obtained by impregnating and molding, and embedding a metal mesh except the opening and reinforcing it with a fiber reinforcing material.

The present invention further covers the opening, which is manufactured by the above-described manufacturing method, with a metal mesh coated with a resin, and except the opening, a metal mesh continuous with the metal mesh of the opening is embedded to generate an electromagnetic wave. A shield is provided.

The electromagnetic wave shield is characterized in that it is reinforced with a fiber reinforcing material except for the openings, and that RIM nylon and cyclopentadiene are used as a matrix resin.

When the resin used for the above reaction injection molding is RIM nylon, a molten lactam containing a polymerization catalyst and a polymerization initiator is injected into a mold, and the polyamide is polymerized by heating the lactam by a monomer casting method. Molded. Examples of the monomer ω-lacmuta include α-pyrrolidone, α-piperidone, ω-enanthlactam, ω-caprolactam, ω-caprylolactam,
ω-pelargonolactam, ω-decanolactam, ω-undecanolactam, ω-laurolactam, c-alkyl-substituted-ω-lacmuta thereof, and a mixture of two or more kinds of these ω-lacmuta. Also,
The ω-lacmuta may contain an improving component (soft component), if necessary. The soft component is a compound having a functional group that reacts with the initiator used in the molecule and has a low Tg, and a polyether having a normal functional group, liquid polybutadiene, or the like is used.

The commercially available raw materials used as the above-mentioned ω-lacmuta include UBE nylon (UX manufactured by Ube Industries, Ltd.).
-21) etc. It is composed of an A component consisting of an alkali catalyst and caprolactam, a prepolymer containing a soft component and a B component consisting of caprolactam.

As the above-mentioned polymerization catalyst, sodium hydride is preferable, but other known .omega.-lacmuta polymerization catalysts such as sodium, potassium, and tylium hydride can be used. The amount added is 0 with respect to ω-lacmuta.
The range of 1-0.5 mol% is preferable. Also, a polymerization initiator
As the (activator), N-acetyl-ω-caprolactam is used, but other triallyl isocyanurates, N-substituted ethyleneimine derivatives, 1.1'-carbonylbisaziridine, oxazoline derivatives, 2- (N- Compounds such as phenylbenzimidoyl) acetanilide, 2- (N-phenylbenzimidoyl) acetanilide, 2-N-morpholino-cyclohexene-1.3-dicarboxanilide, and known isocyanates and carbodiimides can be used. . The amount of the above polymerization initiator added is ω
It is preferably in the range of 0.05 to 1.0 mol% with respect to the amount of lactam.

When a cyclopentadiene resin is used, examples of the polymerizable monomer to be the cyclopentadiene resin include dicyclopentadiene, dihydrodicyclopentadiene, tricyclopentadiene, tetracyclopentadiene, cyclopentadiene-methylcyclopentadiene co-dual body. Etc. are used.

As the polymerization catalyst for the cyclopentadiene resin, halides such as tungsten, molybdenum and tantalum, oxyhalides, oxides, organic ammonium salts and the like are preferably used. As the polymerization initiator, organometallic compounds centered on alkylated metals of metals of groups I to III of the periodic table, oxygen-containing compounds such as alcohols and phenols are preferably used. Furthermore, the solution containing the above-mentioned polymerization catalyst and activator (polymerization initiator) causes the polymerization reaction to start very quickly, so that curing may occur while it does not flow sufficiently into the molding die. Monoether of glycol compound selected from alkylene glycol or polyalkylene glycol as an agent and / or
Alternatively, a monoester is preferably used. Further, upon injection into the mold, it is preferable that the mold temperature is usually in the range of 40 to 130 ° C. and the polymerization reaction is usually performed for 1 to 5 minutes.

When the reaction injection molding resin is used as a matrix resin and is impregnated into a fiber reinforcement, the fiber reinforcement may be carbon fiber, glass fiber, alumina fiber, aramid fiber, silicon carbide fiber, depending on the application. Steel fiber,
Amorphous metal fibers, organic fibers and / or mixtures thereof are preferably used.

[0020]

In the electromagnetic wave shield according to the present invention, since the metal mesh covering the opening and the metal mesh inside the housing are continuous, an electromagnetic wave shield having an opening in which electromagnetic waves are less likely to leak can be obtained. . Further, when the manufacturing method according to the present invention is used, an electromagnetic wave shield having an opening covered with a metal mesh and a metal mesh continuous with the metal mesh embedded in a resin can be manufactured by reaction injection molding in one step. .

Further, since it is manufactured by reaction injection molding,
Since the viscosity of the injection liquid is low, there is no displacement of the metal mesh, and the product as designed can be obtained, and the RIM nylon or cyclopentadiene used in the reaction injection molding method has excellent impact resistance and vibration absorption. Since it also has strength and rigidity, it can be made thin.
Furthermore, since the continuous fibers are also uniformly impregnated, the strength and rigidity can be further improved by these fiber reinforcing materials.

[0022]

The present invention will be described in detail below with reference to the drawings. FIG. 1 shows an electromagnetic wave shield 1 according to the present invention. The electromagnetic wave shield 1 constitutes a part of a housing of a computer terminal device, has a box shape with an opening on the back side, and has a central portion on the front side. It has a rectangular opening 2.

The opening 2 is covered with a metal mesh 3, and the metal mesh 3 is thinly coated with a resin 4 as shown in an enlarged view in FIG. All parts except the opening 2,
As shown in FIG. 3, the metal mesh 3 covering the opening 2 and the continuous metal mesh 3 and continuous fibers 5 are uniformly embedded in the resin 4.

The electromagnetic wave shield 1 is manufactured by the reaction injection molding apparatus shown in FIGS. 10 is an upper mold, 1
Reference numeral 1 denotes a lower mold, and the upper and lower molds 10 and 11 are clamped to form a cavity 12 as shown in FIG. 5. The shape of the cavity 12 corresponds to the shape of the electromagnetic wave shield 1. ing.

On the cavity 12 side of the upper and lower molds 10 and 11, a pair of resin permeation blocking materials (hereinafter, abbreviated as blocking materials) 13 and 14 are provided so as to face each other at a position where the opening 2 is formed. There is. Since the blocking members 13 and 14 are made of rubber having heat resistance and the opening 2 has a rectangular shape, the blocking members 13 and 14 also have a rectangular shape, and the protruding surface thereof is as shown in FIG. The concave portions 13a and 14a and the convex portions 13b and 14b corresponding to the shape of the metal mesh 3 are provided. As shown in FIG. 7, the recesses 13a and 14a are fitted on both sides of the metal wire 3a of the metal mesh 3, and the recesses 13a and 14a are
The resin is allowed to penetrate into the clearance C between the metal wire 3a and the metal wire 14a. On the other hand, the convex portions 13b and 14b are inserted into the void portion 3b (shown in FIG. 2) of the metal mesh 3 and the tip surfaces thereof are brought into pressure contact with each other so as to surely block the resin from penetrating into the void portion 3b. There is.

The lower die 11 is provided with a raw material liquid inlet 15 and a surplus raw material liquid outlet 16 which are open to the cavity 12. Further, a sealing material 17 is attached to the upper end surface which is joined to the upper mold 10.

The process of manufacturing the electromagnetic wave shield using the above apparatus will be described below. First, as shown in FIG. 4, the metal mesh 3 is placed in the cavity 12 of the lower die 11 along the entire cavity die surface. Next, the continuous fiber 5 is placed on the upper surface of the metal mesh 3 except for the portion where the blocking member 14 is provided in a protruding manner. In addition, as the continuous fiber 5,
For example, Toho Rayon Co. carbon fiber cloth W
3101 etc. are used suitably.

After arranging the metal mesh 3 and the continuous fibers 5 in the cavity 3, the upper mold 10 is lowered toward the lower mold 11 and the mold is closed as shown in FIG. At this time, the blocking members 13 and 14 projecting from the upper and lower molds 10 and 11 so as to face each other sandwich the metal mesh 3 from both upper and lower surfaces. That is, the protrusions 13b and 14b of the blocking members 13 and 14 are inserted into the voids 3b of the metal mesh 3 so that the tip surfaces are in pressure contact with each other, while the recesses 13a and 14a of the blocking member are the metal wires 3 of the metal mesh 3.
Insert a from both sides.

Thus, the metal mesh 3 is reliably positioned and held by the blocking members 13 and 14 at the position where the opening 2 is formed.

After the mold is clamped, a reduced pressure is introduced into the cavity 12 and the mold is heated to a required temperature, and in this state, the mixed monomer of RIM nylon is supplied from the raw material solution inlet 15. Since the mixed monomer has a low viscosity and an excellent fluidity, the continuous fibers 5 are uniformly impregnated while filling the voids of the metal mesh 3 in the cavity 12. At that time, in the portion sandwiched by the blocking members 13 and 14, the inflow of the resin is reliably blocked in the void 3b of the metal mesh 3 where the convex portions 13b and 14b of the blocking members 13 and 14 are in pressure contact with each other. On the other hand, since there is a gap C on the outer periphery of the metal wire 3a of the metal mesh 3 surrounded by the recesses 13a and 14a of the blocking members 13 and 14, the resin penetrates into the gap C and a thin film is formed by the resin. .

After injecting the mixed monomer, the inside of the cavity is maintained for a required time at a required pressure to complete the polymerization reaction.

In the above embodiment, the continuous fibers are embedded and reinforced except for the openings, but it is not always necessary to fill the fiber reinforcing material. However, when a fiber reinforcement material, especially continuous fiber is filled, strength and rigidity are improved,
The thickness of the molded product can be reduced accordingly.

[0033]

EXPERIMENTAL EXAMPLE An electromagnetic wave shield according to the present invention and an electromagnetic wave shield having a separate metal mesh attached to the opening were provided, and a comparative test was conducted on the shielding effect. Embodiment of the present invention: 1 in a 20 cm × 20 cm plate-shaped housing
An opening of 0 cm × 10 cm is provided, and a continuous metal mesh of steel 16 mesh is arranged in the plate-like housing and the opening. Comparative Example: A 20 cm × 20 cm plate-shaped housing (in which a steel 16 mesh is embedded) is molded, and an opening of 10 cm × 10 cm is cut out in the plate-shaped housing, and a metal mesh of steel 16 mesh is formed in the opening. To be attached later. Test method: The shield effect of the electric field component at 100 MHz and 500 MHz was measured by the Advantest method. Test results: The above measurement results were as shown in Table 1 below.

[0034]

[Table 1] Shielding effect test result (unit: dB) 100 MHz 500 MHz Example 75 70 Comparative example 50 10

The present invention is not limited to the above-mentioned embodiment, and instead of the metal mesh, a perforated metal plate made of punching metal may be used as long as it has a shield effect and a heat dissipation opening. Good.

[0036]

As is apparent from the above description, in the electromagnetic wave shield according to the present invention, the metal mesh or the porous metal plate stuck to the opening is the metal mesh or the porous metal plate embedded inside the housing other than the opening. Since it is continuous, there is little leakage of electromagnetic waves and it is excellent in terms of shielding effect.

Also, by reaction injection molding, in one step,
It is possible to manufacture an electromagnetic wave shield in which an opening is covered with a metal mesh or the like, and a metal mesh or the like continuous with the metal mesh or the like is embedded inside a resin. In this way, a separate step for covering the opening with a metal mesh or the like, which has been conventionally required, is not required, the working efficiency is improved, and the cost can be reduced accordingly.

Further, since the metal mesh or the like covering the opening is continuous with the metal mesh or the like embedded in the resin, it does not come off from the opening. Further, since the metal mesh etc. that covers the opening is also covered with the resin, there is an advantage that rust is unlikely to occur.

Further, R which is reaction injection molded as resin
Since IM nylon, cyclopentadiene and the like are used, strength, rigidity, vibration absorption and impact resistance can be improved. Furthermore, the resin to be subjected to reaction injection molding has low viscosity and excellent fluidity, and therefore can be easily molded using continuous fibers or the like as a reinforcing material. As described above, by improving the strength and the rigidity, the electromagnetic wave shield has various advantages such as a reduced thickness.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view of an electromagnetic wave shield according to the present invention.

FIG. 2 is an enlarged perspective view of a metal mesh.

FIG. 3 is a horizontal sectional view of the electromagnetic wave shield of FIG.

FIG. 4 is a schematic cross-sectional view showing an apparatus for manufacturing the electromagnetic wave shield of FIG.

5 is a schematic cross-sectional view of the manufacturing apparatus of FIG. 4 with the mold closed.

FIG. 6 is a perspective view of essential parts of the tip portions of the resin permeation blocking materials 13 and 14 shown in FIG.

FIG. 7 is a cross-sectional view showing a fitted state of the resin permeation blocking materials 13 and 14 and the metal mesh 3.

[Explanation of symbols]

 1 Electromagnetic Wave Shield 2 Opening 3 Metal Mesh 4 Resin 5 Continuous Fiber 10 Upper Mold 11 Lower Mold 12 Cavity 13,14 Resin Permeation Blocker

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location B29K 105: 34

Claims (5)

[Claims] 1. An inside of a resin obtained by reaction-molding an opening covered with a metal mesh or a porous metal plate, and except the opening, the metal mesh of the opening or the metal mesh continuous with the porous metal plate or the porous metal plate. Electromagnetic wave shield embedded in the. 2. The resin is made of RIM nylon or cyclopentadiene, and a metal mesh or a porous metal plate covering the opening is coated with the resin, and the resin except the opening is reinforced with a continuous fiber reinforcing material. The electromagnetic wave shield according to claim 1, wherein 3. A metal mesh or a perforated metal plate is previously placed in the cavities of a pair of upper and lower molds for reaction injection molding, and then the molds are clamped so as to project from the upper and lower molds facing the cavity. The pair of resin permeation barriers thus sandwiched partially sandwich the upper and lower surfaces of the metal mesh or porous metal plate, and then inject the unreacted raw material liquid into the cavity to cause a polymerization reaction. The part sandwiched by the permeation barrier is an opening covered with a metal mesh or a porous metal plate, and the other part is a metal mesh or a porous metal plate continuous with the metal mesh of the opening or the porous metal plate inside the resin. A method for manufacturing an electromagnetic wave shield in which is embedded. 4. The method according to claim 3, wherein the pair of resin permeation blocking materials are made of a heat-resistant elastic material having an uneven surface for fitting with a metal mesh or a porous metal plate on the surface. 5. Inside the cavity of the mold, a portion other than a portion to be an opening by the resin permeation blocking material,
The fiber reinforced material is arranged in advance, is molded by being impregnated with a resin to be injected into the cavity, and a metal mesh or a porous metal plate is embedded except for the opening and is reinforced with the fiber reinforced material. 5. The method for producing an electromagnetic wave shielding material according to any one of 3 and 4.