JPH05347493A - Electromagnetic shielding material and molding method therefor - Google Patents

Abstract

PURPOSE:To manufacture a desired shape shielding material with ease by setting in a desird shape mold a host material sheet yielded by melting and jetting a conductive metal material into a flexible relatively noble three-dimensional texture mesh structure, and heating and molding of the same. CONSTITUTION:Melted droplets 1 of conductive metal are jetted from a welding apparatus head H into a flexible relatively noble unwoven fabric or sponge three-dimensional texture 2. The conductive metal includes zinc, aluminum, and alloys of the formers, carbon steel, stainless steel, brass, bronze, and copper, etc., which are melted in the melting head H into fine powder and jetted. The metal fine powder enters among the texture 2 and into the same to provide a sheet configuration. The sheet is set in a desired shape metal mold, and heated and pressurized into a desired shape. Hereby, electromagnetic shielding materials of various shapes are manufactured with ease.

Description

Detailed Description of the Invention

[0001]

[Object of the Invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic wave shielding material and a molding method thereof which can be fitted in a housing of various electronic devices or used as a housing itself to prevent accidents, malfunctions and the like due to electromagnetic wave noise. Is.

[0002]

Recently, electronic devices to which digital circuits are applied are used everywhere. For the purpose of insulation, the housings of these electronic devices are often made of plastics which are lightweight, excellent in workability and durability, and inexpensive. However, since plastic originally has high electromagnetic wave permeability, many I
Electromagnetic noise due to high-frequency pulses generated from C and LSI is radiated to the outside of the housing, which causes image distortion on TV, malfunction of online computers such as banks, malfunction of various automatic control devices, and electronic circuits built in itself. Another problem is electromagnetic interference, which causes malfunction by receiving electromagnetic noise from other electronic devices. In addition, due to its high insulating property, the plastic housing is easily charged with static electricity, and the noise generated when this static electricity discharges also causes malfunctions and directly damages electronic devices. There is.

For this reason, in addition to primary processing in which various conductive fillers are mixed in at the raw material stage of plastic, conductive paint is applied to the plastic housing, metal spraying, vacuum deposition, sputtering, electroless plating are performed. ,
Secondary processing such as electroplating and sticking metal foil is performed. However, when a conductive filler is mixed in at the raw material stage of plastics, problems such as deterioration of moldability and physical properties occur, and the plastic housing is directly coated with conductive paint, metal spraying, vacuum deposition, plating, etc. In that case, there is a concern that some of them may come off and short-circuit the circuit.In addition, pre-processing and post-processing of undercoat and overcoat are required, and process management is complicated. Had. In particular, the method using metal spraying has the advantage that the electromagnetic wave shielding effect is high, but since it was a method of processing directly on the plastic housing, there is a high risk that the product will warp or the film will peel off. The total cost tended to be high as inevitable.

[0004]

Therefore, the present invention has been made in view of such a background, and the portion that controls the electromagnetic wave shielding function is an independent member, that is, a sheet shape or a desired shape. Obtained as an electromagnetic wave shielding material, while securing a high electromagnetic wave shielding property due to metal spraying, avoiding the risk of product warping or film peeling off, it can be fitted inside the existing housing or used as a housing itself. It was made possible.

[0005]

Structure of the Invention

That is, the electromagnetic wave shielding material according to the first invention of the present application has a layer in which a conductive metal material is sprayed on a flexible and relatively bulky three-dimensional network structure. Is characterized by.

A method of molding an electromagnetic wave shield material according to a second invention of the present application is a step of spraying a conductive metal material on a flexible and relatively bulky three-dimensional network structure body to obtain a base material sheet, And a step of forming the base material sheet into a desired shape by thermoforming.

Further, a method of molding an electromagnetic wave shielding material according to a third invention of the present application is a step of spraying a conductive metal material on a flexible and relatively bulky three-dimensional net structure to obtain a base material sheet. And a step of thermoforming the base material sheet to obtain a shaped body having a desired shape, and a step of setting the shaped body in a cavity of an injection mold and then setting a core and injecting a molten synthetic resin And having.

Further, the method for forming an electromagnetic wave shielding material according to the fourth invention of the present application comprises the steps of spraying a conductive metal material on a flexible and relatively bulky three-dimensional network structure to obtain a base material sheet. , The base material sheet is set between a core and a cavity in an injection mold, and the base material sheet is pressed into the cavity by the core while heating and softening the base material sheet, and a synthetic resin melted from a runner formed in the core is set. And a step of injecting.

Further, a method of forming an electromagnetic wave shield material according to a fifth invention of the present application is a step of spraying a conductive metal material on a flexible and relatively bulky three-dimensional network structure body to obtain a base material sheet. Setting the other resin sheet on the base material sheet in a molding die and heating them to perform compression molding with the base material sheet and the other resin sheet softened. Is characterized by. These inventions are intended to achieve the above object.

[0010]

In the present invention, the conductive metal material flies as droplets on the flexible and relatively bulky three-dimensional network structure, and adheres to the three-dimensional network structure as fine droplets. this is,
Part of it penetrates the inside of the layer and adheres in the deep part,
This is not only on the surface but also in the layer direction of the relatively bulky three-dimensional network structure. As a result, if this is used as an electromagnetic wave shield, electromagnetic waves will be generated between droplets in the three-dimensional network structure. Is attenuated and absorbed by repeating three-dimensional reflection. In addition, since the droplets of the conductive metal material are porous, they do not break even when bent, and the three-dimensional net body base can be integrally deformed and followed, and easily formed into a desired shape by thermoforming. In addition, it is possible to improve the bulkiness and to confine the droplets in a film.

[0011]

EXAMPLES Next, the present invention will be specifically described with reference to the illustrated embodiments and the embodiment method using the illustrated apparatus, but before that, the thermal spraying and the three-dimensional network structure which are the constituent elements will be described a little. In other words, thermal spraying is a technology that melts a wire or rod-shaped linear material or powder material at high temperature and sprays it as a droplet onto the object to be processed, forming a film that is a stack of the droplets on the surface of the object. It is well known as a metal rust preventive means or a means for directly imparting conductivity to a plastic housing. There are various types of this thermal spraying, such as flame type, arc type, plasma type, etc., depending on the means for melting the material, and depending on the material form at that time, wire type, rod type, powder type, etc. Subdivided. In the present invention, any of these forms and any form can be applied. Among them, in the flame spraying method, the temperature of the droplet is relatively low, and the material of the three-dimensional network structure is generally heat. It is preferable because it is not so strong, and as an enforcement method,
There are a stationary type and a manual type, but the stationary type enables mass production, and the manual type enables field work.

Further, as the thermal spray material, generally, zinc, aluminum and alloys thereof, carbon steel,
Low alloy steel, stainless steel, havit, molybdenum, brass, brass, aluminum bronze, manganese bronze, copper, nickel aluminite, monel, nickel, tin, lead, etc. are used, but in the present invention, conductive High metal materials are preferred. Of course, among these, the temperature is selected in consideration of the balance between the droplet temperature, the generation of rust after depositing as droplets, the adhesion strength, the cost, and the like. It should be noted that these conductive metal materials may be directly sprayed onto the three-dimensional network structure, but if the adhesive strength or the adhesion strength is insufficient directly, it may be improved by applying a primer or the like in advance. In addition, it is also possible to devise such as overlapping droplets of different materials.

The three-dimensional network structure to be sprayed is a so-called non-woven fabric or sponge, which is a flexible and relatively bulky breathable material, and has a network structure into which droplets can penetrate. It is a thing. In addition, as the method for producing the non-woven fabric, there are a dry method such as an adhesive method, a spun lace method, a spun bond method, a melt blown method, a needle punch method, and a stitch bond method, and a so-called wet method for manufacturing so-called paper. However, the nonwoven fabric applicable to the present invention may be manufactured by any one of them, but it is required that it is bulky and capable of allowing droplets to penetrate and adhere even inside. Further, the so-called sponge body may have any foaming mechanism such as chemical foaming or mechanical foaming, but it is suitable that it has a large number of open cells, and further, a film-like body between cells. It is preferable to remove only the network structure and leave only the network structure.

The material of these three-dimensional network structures is not particularly limited, but polyethylene,
Various thermoplastics such as polyurethane, polypropylene, polyvinyl chloride, polyvinylidene chloride, polyamide 6, polyamide 66, polycarbonate, polyimide, phenol resin, urea resin, melamine resin, silicone resin, epoxy resin, unsaturated polyester resin, acrylic resin, etc. , Thermosetting resins, and modified or composite resins thereof, various kinds of materials can be applied with the network structure forming mechanism, the conductive metal material, the thermal spraying conditions and the like being adjusted.

As the three-dimensional network structure, specifically, for example, a molten thermoplastic resin is blown into a thread form from a die having a porous die by a high-temperature and high-speed air flow, and the fibrous resin is placed on a conveyor. There is a non-woven fabric "TAPYRUS (trade name)" manufactured by Tonentapyrus Co., Ltd. by the Melt-Blowing method, which is a type of jet spinning method that accumulates and forms a web of self-adhesive ultrafine fibers with no binder. "Everlight Scott (trade name)" made by Bridgestone Co., Ltd. that chemically removes the film between the bubbles and leaves only the network structure.
There is.

In FIG. 1, reference numeral 2 is a non-woven fabric which is a flexible and relatively bulky three-dimensional mesh body. A thermal spraying apparatus head H is opposed to the non-woven fabric 2 and the head H is shaken to conduct electricity evenly. Zinc as a metallic material was sprayed. At this time, zinc, which is a conductive metal material, flies into fine droplets 1 by heating and a jet stream in the thermal spraying device, and adheres to each fiber forming the nonwoven fabric 2. This partly penetrates into the inside of the layer and adheres in the deep part, and is distributed and adhered not only on the surface but also in the layer direction of the relatively bulky three-dimensional network structure. Then, a part of the remaining part permeates the nonwoven fabric 2 and becomes a state of permeating to the back surface. Then, if necessary, repeat thermal spraying from the back side,
Apply droplets evenly. In addition, the adhesion of the droplet is
Although it is formed as a thin layer though it is thin, it is porous because it is originally composed of overlapping droplets. In addition, when masking is performed during spraying by using a mask, a parting from the surrounding is made, and it is possible to clearly form a portion with a droplet layer and a portion without a droplet layer.

The non-woven fabric 2 formed by adhering the droplets 1 thus obtained has zinc droplets distributed in the layer direction of the relatively bulky non-woven fabric.
In the tissue, the droplets 1 are repeatedly reflected three-dimensionally between the droplets 1 and are attenuated, and an excellent electromagnetic wave shielding effect is achieved. In addition, since the droplet 1 is porous, it does not break even when bent, and the nonwoven fabric 2 can integrally follow the deformation, and can be easily arranged in a space with curved concavities and convexities. Sound absorption, heat insulation,
It can be used as an electromagnetic wave shielding material that can also provide a vibration damping effect. Hereinafter, this is referred to as a base material sheet S.

The base material sheet S, which is one mode of the electromagnetic wave shielding material, can be used as it is as described above, but as described below, it is used by shaping it into a desired shape by pressing or thermoforming. You can FIG. 2 shows a state of being compressed by a pressing machine, in which the base material sheet S is spread and compressed as it is by the pressing machine P. As a result, the original thickness becomes thin and a high density state is achieved. In this case, the base material sheet S tries to return to its original bulky state because the fibers themselves have some elasticity, but since the droplets 1 are porous, they follow the compression of the nonwoven fabric 2. Moreover, the restoration is suppressed and FIG.
A high density state 2a as shown in (a) can be obtained. Further, by using a heat press machine as a press machine, or by arranging a heating means in the mold, the degree of heating and the timing of pressurization can be controlled, and as shown in FIG. 3 can be formed, or the entire film can be formed into a film 3f as shown in FIG. If the skin layer 3 is formed in this way or the whole film is made into a film 3f, the droplet 2 will be in a state of being confined in the film-formed layer, and will not drop off thereafter, and the circuit will be short-circuited. The risk of causing an accident is further reduced. In addition, if the thermal spraying is performed only from one surface and the skin layer is formed only on the surface not sprayed,
Since there are few droplets on the skin layer side, the droplets can be prevented from falling off during use in a higher dimension.

The base material sheet S pressed in this way is compressed to improve its bulkiness, and yet the droplets of the conductive metal material remain adhered to the inside, but rather the compressed network Since it is blocked and held by, the electromagnetic wave shielding effect remains the same, and it can be used in the same manner as the base material sheet S, or can be used by being attached along the housing. Furthermore, if a part of the thin layer is made into a film by forming a skin layer,
The thermoforming by vacuum pressure or compressed air pressure can be directly dealt with. Further, even if the skin layer is not formed, if a separate film is superposed on the skin layer, the thermoforming can be similarly performed. Therefore, the base material sheet that has been subjected to the above-mentioned press working is hereinafter referred to as a forming sheet A.

The molding sheet A thus obtained can be shaped into a container by thermoforming, for example, as shown in FIG. In FIG. 4, 3 and 3 are the skin layers of the molding sheet, and 2a is the high-density portion. That is, the sheet shaped body B is formed by thermoforming from molding sheets having upper and lower skin layers. The sheet shaped body B can be obtained by the thermoforming shown in FIGS. 5 to 7, and at the stage of the press working, it is not a flat die but a hot die having a pair of upper and lower concavities. It can also be obtained by pressing.

Various methods can be used to obtain the sheet shaped body B by thermoforming the molding sheet A. That is, what is shown in FIG. 5 shows a state in which the forming sheet A heated and softened by a heater is placed on the female die 4 and shaped by a vacuum forming method (straight method) in which the sheet is sucked in a vacuum. Further, what is shown in FIG. 6 is a vacuum forming method (a drape method) in which the forming sheet A heated by the heater is pushed up by the mold 5 to perform pre-expansion, and then the sheet is sucked and formed in a vacuum in a mold. In addition to these vacuum forming methods, as shown in FIG. 7, a forming sheet A is sent between the heating plate 6 and the mold 7, and compressed air E is pressed while pressing the forming sheet A with the heating plate 6. It is also possible to adopt a pressure molding method in which the molding sheet A is sent and pressed against the mold 7 to mold. In addition, although not shown, a combination of a vacuum forming method and a pressure forming method can be performed. As the forming sheet A for these thermoformings, a sheet having the skin layer 3 formed on only one surface was used.

The sheet shaped body B thus obtained
Can be used by fitting it in a plastic housing,
In order to use itself as a housing or to further enhance the shape retention, insert molding or outsert molding can be performed as described below. That is,
The method shown in FIG. 8 uses an injection molding method,
As shown in FIG. 8A, the sheet shaped body B is set in the cavity 8 with the high-density state 2a side facing outward, that is, the side on which the core is set. Then, as shown in FIG. 8B, the core 9 is pushed into the cavity 8 to a predetermined position, and the synthetic resin melted from the runner 10 in the core 9 is poured into the gap between the sheet shaped body B and the core 9 for cooling. Let it solidify. In this way, the poured resin integrally covers the surface of the sheet shaped body B, and a molded body having a relatively thick cross section can be obtained.

In the above embodiment, the sheet shaped body B is previously prepared.
Although the method of shaping and setting each of them in the cavity 8 is adopted, the following continuous method of performing shaping and injection together can also be adopted. That is, as shown in FIG. 9, a high density state 2 between the cavity 8 and the core 9 is obtained.
The continuous tape of the molding sheet A is set so that the core a side is the core 9 side so that the tape can be sequentially fed out, and the heating means 11 is also exposed to this. Core 9 in this state
Is pressed against the forming sheet A, and the cavity 8 is
Continue pressing to the inside to mold. Then, the molten synthetic resin is poured from the runner 10 to form a surface integrated with the high density state 2a side of the molding sheet A. When a series of molding and injection operations are completed in this way, the molding sheet A is sequentially fed and the same operation is repeated again to continuously obtain a molded body C. Incidentally, the thus continuously molded product can be used as a carrier tape or the like for electronic parts.

Next, as another method for forming the layer of the thick synthetic resin on the base material sheet S or the molding sheet A, a method in which a compression molding method is applied will be described. First, FIG. 10 (a)
As shown in, the prepreg 12 in which the reinforcing fiber is impregnated with the thermosetting resin is superposed on the molding sheet A. As shown in FIG.
And the female die 14, and the heating die 13 presses the prepreg 12 and the molding sheet A into the female die 14 to shape the prepreg 12 and the molding sheet A into the shape of the female die 14 and heat. A molded product C of the fiber-reinforced resin that is integrated with the molding sheet A is obtained by curing.

The plastic housing in electronic equipment is not limited to a box-shaped one, but includes complicated shapes such as children's toys in which digital circuits will be increasingly applied in the future. Further, instead of being applied to a small housing, it can be shaped like a so-called tent and used as a computer room, a control room or the like. Considering these moldability, it is particularly advantageous that the base material sheet is flexible and relatively bulky. Further, the degree of thermal spraying may be determined depending on the required performance as an electromagnetic wave shielding material, that is, static electricity removal and the magnitude of the electromagnetic wave shielding effect. Further, in the above-mentioned examples, a nonwoven fabric was used as the three-dimensional mesh structure, The invention is not limited to this,
Of course, even a sponge body can be similarly applied.

[0026]

As described above, according to the method of the present invention, a base material sheet capable of imparting conductivity to a housing of an electronic device and exhibiting an electromagnetic wave shielding effect in an extremely simple process, Molding sheet, sheet shaped body, it is possible to obtain an electromagnetic shielding material of each aspect of the molded body, also,
The electromagnetic wave shielding material of the present invention is an independent member per se, and in addition to having electromagnetic wave shielding properties, it is also rich in subsequent moldability, and can be formed into a skin layer and a film to trap droplets. Further, it can be obtained as a molded product having good shape retention and low strength, and can be used as it is as a housing. Therefore, it can greatly contribute to solving the problem of electromagnetic noise of electronic devices, which is now a major social problem.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a state in which a conductive metal material is sprayed on a nonwoven fabric.

FIG. 2 is an explanatory diagram showing a state in which a base material sheet is pressed.

FIG. 3 is a cross-sectional view showing each aspect of a molding sheet obtained by pressing.

FIG. 4 is a perspective view showing a sheet shaped body by partially peeling it off.

FIG. 5 is an explanatory view showing step by step how a forming sheet is shaped into a desired shape by a vacuum forming method (straight method).

FIG. 6 is an explanatory view showing, step by step, how a shape is formed by the vacuum forming method (drape method).

FIG. 7 is an explanatory view showing, step by step, how a shape is formed by the pressure forming method.

FIG. 8 is an explanatory diagram showing a state in which a synthetic resin layer is formed on a sheet shaped body by an injection molding method, separately for each set state of the sheet shaped body and the state of molding.

FIG. 9 is a skeletal longitudinal side view showing an embodiment in which shaping of a molding sheet and injection of a synthetic resin are simultaneously performed.

FIG. 10 is an explanatory view showing step by step how a resin layer is formed on a molding sheet by a compression molding method.

[Explanation of symbols]

 S Base material sheet A Sheet for molding B Sheet shaped body C Molded body H Thermal spraying device head E Compressed air P Press machine 1 Conductive metal material droplet 2 Nonwoven fabric 2a High density state 3 Skin layer 3f film 4 Female type 5 mold 6 Heating Plate 7 Mold 8 Cavity 9 Core 10 Runner 11 Heating Means 12 Prepreg 13 Heating Press Mold 14 Female Mold

Claims (5)

[Claims] 1. An electromagnetic wave shielding material comprising a flexible and relatively bulky three-dimensional network structure having a layer formed by spraying a conductive metal material. 2. A step of spraying a conductive metal material onto a flexible and relatively bulky three-dimensional network structure to obtain a base material sheet, and thermoforming the base material sheet to shape it into a desired shape. And a step of forming the electromagnetic wave shield material. 3. A step of thermally spraying a conductive metal material onto a flexible and relatively bulky three-dimensional network structure body to obtain a base material sheet, and thermoforming the base material sheet to obtain a shaped article having a desired shape. And a step of setting the shaped body in a cavity of an injection molding die, setting a core, and injecting a molten synthetic resin. 4. A step of spraying a conductive metal material onto a flexible and relatively bulky three-dimensional network structure to obtain a base material sheet, and the base material sheet comprising a core and a cavity in an injection molding die. And a step of injecting a molten synthetic resin from a runner formed in the core while pressing the base material sheet into the cavity while heating and softening the base material sheet, and molding the electromagnetic wave shielding material. Method. 5. A step of spraying a conductive metal material onto a flexible and relatively bulky three-dimensional network structure to obtain a base material sheet, and molding in a state where another base material sheet is superposed on the base material sheet. A step of setting in a mold and heating these to perform compression molding in a state where the base material sheet and other resin sheets are softened.