JPS61240698A - Molding for electromagentic wave shielding property - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a molded product having electromagnetic shielding properties suitable for use in structures such as housings of various electronic devices and electronic parts.

[Conventional technology]

In recent years, with the development of electronic devices such as office automation equipment, computer equipment, and communication equipment that incorporate ICs and LSIs, electromagnetic waves generated by various electronic devices can interfere with the functions of other devices and interfere with their normal operation. becoming a major problem. Synthetic resins or rubber-like materials are widely used as housing materials for various electronic devices and as structural materials for electronic components, but because they themselves are electrically insulating, they do not have the ability to shield electromagnetic waves. For the purpose of imparting electromagnetic wave shielding ability, various electrically conductive processing methods have been attempted on synthetic resins or solid materials (hereinafter collectively referred to as molding raw materials). That is, methods have conventionally been used in which a conductive coating is formed on the inner surface of a molded product made using these molding raw materials by applying a conductive paint or by thermally spraying a metal. However, with these methods, it is difficult to uniformly form a conductive film on the inner surface of a molded product that has uneven or curved parts, and the adhesion strength between the molding raw material and the conductive film is not sufficient.
There is a risk that the electromagnetic wave seal 1' may be partially peeled off and the electromagnetic wave sealing properties may be lost, or that the internal electric circuit may be harmed. There is also a method of mixing conductive fillers such as metal fibers or metal flakes into the molding raw material to make the molding raw material itself conductive. Although this method is highly suitable for mass production and can produce conductive molded products in one step, it is difficult to uniformly disperse the conductive filler, and the screw of the injection molding machine is easily damaged by the conductive filler. Another disadvantage is that since the conductive filler is exposed on the outer surface of the molded product, it is necessary to paint it to modify the appearance.

Furthermore, in order to attach electronic components or the like inside the molded product, it is generally necessary to provide an electrically insulating protrusion on the inner surface of the molded product. To achieve this, in both of the above two electrically conductive processing methods, conductivity is imparted to the entire inner surface of the molded product, so it is necessary to mask only the portion that is desired to be insulating.

In this case, especially in the former conductive processing method, since the conductive film is lost only in the masked portion, there is a risk that electromagnetic waves will leak from that portion and the electromagnetic wave shielding performance will be greatly reduced. Moreover, masking and demasking operations are labor-intensive and complicated.

[Problem that the invention seeks to solve]

The purpose of the present invention is to solve the above-mentioned problems of conventionally known molded products with electromagnetic shielding properties, and to provide a durable electromagnetic shield even for molded products with curved surface parts having various curvatures. The object of the present invention is to provide a molded product having electromagnetic shielding properties that is easy to manufacture and that can maintain its properties and is provided with an electrically insulating protrusion inside.

[Means for solving problems]

An object of the present invention is to provide a molding material made of a synthetic resin or a rubber-like material, in which a conductive fabric material having a large number of gaps through which the molding material can pass when molding the molded product is At least one protrusion formed from the molding raw material is provided on at least one surface of the molded product. This is achieved by a molded product that has electromagnetic shielding properties.

The present invention will be described in detail below with reference to the accompanying drawings showing an embodiment of a molded product having electromagnetic shielding properties according to the present invention.

FIG. 1 shows a perspective view of an embodiment of a molded product having electromagnetic shielding properties according to the present invention.

The molded product 1 shown in FIG. 1 includes a base part 2 made of a molding raw material made of synthetic resin or rubber-like material, and a base part 2 disposed inside the base part 2 along the surface of the base part 2 and integrally with the molding raw material. Further, a protrusion 4 is provided on the inside of the base body 2 beyond the conductive fabric 3. FIG. 2 shows a part of the cross section of the molded product 1 shown in FIG. It is formed by being Therefore, the conductive fabric 3 is not exposed on the surface of the protrusion 4 but is embedded in the molding material, and as a result, the electrical insulation in the protrusion 4 is maintained. On the other hand, conductive fabric material 3
are arranged continuously along the inside of the molded product 1, so that electromagnetic shielding properties are maintained.

The shape and number of the protrusions may be arbitrarily determined depending on the shape and number of electronic components when installing the electronic components inside the molded product, and the shape and number of the protrusions 4 shown in FIG. It is not limited to. However, when attaching electronic components to the inner surface of a molded product whose inner surface is conductive via insulating protrusions, the surface other than the protrusions is conductive, so if the height of the protrusions is low, there will be no conduction between the electronic components and the parts. There is a risk of contact with the internal genital surface. In order to prevent such a risk, it is preferable that the height of the protrusion is 3 mm or more.

In addition, when forming insulating protrusions on a molded product whose inner surface has been made conductive by applying conductive paint or spraying metal,
Masking must be performed as described above. Therefore, no conductive film is present in the portion corresponding to the bottom area of the protrusion. In particular, if the maximum diameter of the bottom surface of the protrusion (indicated by the maximum distance across the bottom surface) is 5 mm or more, the leakage of electromagnetic waves (frequency 100MILZ to 1000M100O) will be severe, and the electromagnetic wave shielding property will be greatly reduced.However, the electromagnetic wave shielding property according to the present invention As mentioned above, in a molded product having a protrusion, the protrusion is formed on the conductive fabric, so the protrusion can be of any size depending on the shape of the electronic component etc. to be attached, for example, the maximum size of the protrusion on the bottom surface of the protrusion. Even if the diameter is 5 mm or more, the electromagnetic shielding property will not deteriorate.

Molding raw materials used in the molded product having electromagnetic shielding properties according to the present invention include thermoplastic synthetic resins such as ABS resin, polystyrene resin, modified PPE resin, and polyolefin resin, thermosetting four-curing resins such as phenol resin and polyester resin, and butadiene resin. A rubber material made of synthetic rubber such as polyolefin rubber or polyolefin rubber can be used.

The conductive fabric used in the molded product having electromagnetic shielding properties according to the present invention refers to a knitted fabric or a nonwoven fabric imparted with electrical conductivity. The imparting of conductivity can be roughly divided into the following three types.
Two methods can be used.

■ Perform conductive treatment on insulating fabrics by metal plating, metal spraying, vacuum coating, etc.

(2) A conductive fabric is made using insulating fibers or threads that have been subjected to conductivity treatment in the same manner as in (2) above, or conductive fibers or threads such as metal fibers or carbon fibers.

(2) A conductive fabric is made using yarn obtained by covering or twisting conductive fibers with insulating fibers.

However, even fabrics made by methods other than those described above can be used to form the molded product of the present invention as long as they have conductivity.

As the material for the insulating fabric or fiber, any organic fiber such as natural fiber, recycled fiber, or synthetic fiber, or inorganic fiber such as glass fiber can be used. Note that highly elongated yarns such as undrawn yarns and semi-drawn yarns of synthetic fibers can be used. As the conductive treatment method, a metal plating method is preferable because it is lightweight, has good conductivity, and has strong adhesion of the metal film. Good electromagnetic shielding (100 MI
The electric field strength is 30 in the frequency range from lz to 1000100O.
In order to obtain attenuation of dB or more, the conductive fabric must be
It is desirable to have a surface resistance of 0Ω/Ca or less.

The conductive fabric used in the molded product with electromagnetic shielding properties according to the present invention must have a gap large enough to allow the molding material in a flowable state by melting etc. to enter and penetrate. It is. Therefore, the method for manufacturing a molded product having electromagnetic shielding properties according to the present invention will be described below, including the meaning of clarifying the necessity of the gap.

The molded product having electromagnetic wave shielding properties according to the present invention is produced by placing a conductive fabric in a mold in advance, and using an injection molding machine or the like to melt the molding material in a flowable state and press it into the mold at high pressure. It can be obtained by introducing it by injection or the like and then cooling or heating to harden it. In other words, when a conductive fabric is placed in a mold and, for example, a molten molding layer material is injected, the fabric is pressed against the inner surface of the mold on the opposite side of the gate by the pressure of the molding material, and the mold deforms along the shape of. By curing the molding raw material as it is, an integrally molded product having a conductive fabric bonded to the surface portion is formed.

However, if there is an open part with a large curvature that prevents the fabric from entering the mold on the opposite side of the gate, the molding material that has penetrated the gap in the structure of the fabric will enter this part and form a protrusion. will be formed. In order to mold the conductive fabric integrally with the molding raw material and form the protrusions on the opposite side of the conductive fabric, as described above, the conductive fabric must contain the molding raw material. A gap large enough to penetrate and penetrate is required.

When the conductive fabric is a knitted fabric, the structure is flexible, so when it is stretched along the mold, the gap between the structures widens, and the molding material slips through the gap. It is easy to understand.

In the case of a woven fabric, since the structure is rigid, it is necessary to use a woven fabric that has a certain amount of space between the fiber structures. In this case, the maximum diameter of the gap (maximum across distance) is 0.
If the size is 3 mm or more, the molding material can sufficiently penetrate and penetrate. However, for example, 100 to 1
In order to obtain good electromagnetic shielding properties at 000100O, it is preferable that the maximum diameter of the gap does not exceed 5 mm.

Generally, a housing for electronic equipment is a three-dimensional structure having a curved surface portion having various curvatures and a flat portion.

In the present invention, since a conductive fabric with high flexibility and stretchability is used as the conductive material, it can flexibly follow various curved surfaces of the mold, and can be applied to the entire surface along the complex shape of the molded product. It is possible to provide uniform conductivity.

When a conductive fabric is stretched during molding,
Initially, the fabric is stretched due to its structure, and then the threads are stretched and finally break. At this time, when a knitted fabric made of spun yarn is used as the conductive fabric, the short fibers become separated not only when stretched by the tissue but also when the yarn bodies are stretched, maintaining conductivity until just before breaking. Gender is preserved.

Therefore, by using a conductive knitted fabric made of spun yarn that has a breaking elongation greater than the elongation when stretched along the inner surface of the mold of a molded product, conductivity can be imparted uniformly over the entire surface of the molded product. be able to.

When using a knitted fabric of long fibers obtained by conductive treatment as a conductive fabric, the conductivity is maintained when stretched by the tissue, but the conductive material is cut when the threads are stretched. , separation greatly reduces conductivity.

Therefore, in this case, when using a conductive knitted fabric made of long fibers that has a tissue elongation rate that is higher than the elongation rate when stretched along the inner surface of the mold of the molded product, the conductive fabric can be uniformly conductive over the entire surface of the molded product. can be granted. On the other hand, metal fiber,
In the case of knitted fabrics made of long fibers such as carbon fibers, conductivity is maintained up to the elongation at break. All you need is to have it. Conductive woven fabrics and nonwoven fabrics made of long fibers have a low elongation rate due to their structure, so it is not preferable to use them for molded products with large curvature.

In the molded product having electromagnetic shielding properties according to the present invention, a part of the molding raw material enters or penetrates the gap between the conductive fabrics, so the conductive fabric firmly adheres to the molded product due to the anchor effect. .

In particular, when a knitted fabric made of spun yarn is used, the fluff of the spun yarn and the synthetic elastomer are intertwined with each other, resulting in a very high adhesion strength.

〔Example〕

Hereinafter, specific examples of molded products having electromagnetic shielding properties according to the present invention will be shown in comparison with comparative examples.

Actual difference ■Acrylic fiber fabric made of top-spun yarn (Cashmilon manufactured by Asahi Kasei Industries, Ltd.) 30'Nm, plain weave using triple threads, weaving density (
Electroless nickel plating was applied to 70 mm length/50 mm width) to obtain a conductive fabric having a nickel deposition amount of 20 g/m2 and a surface resistance of 0.16 Ω/crl. The elongation at break was 16% in the vertical direction and 23% in the horizontal direction. This fabric-like material was placed between a pair of molds shaped like the bottom lid of a calculator, and was sandwiched between the molds on both sides, so that the periphery of the fabric-like material was tightly fixed. The degree of elongation of the mold in the vertical and horizontal directions (the ratio of increase in length along the inner surface of the mold to the length of a straight line connecting both ends of the inner surface of the mold) was 12% and 15%, respectively. A modified PPE resin (Zylon R manufactured by Asahi Kasei Industries, Ltd.) was injected from the front side of the bottom lid of the calculator using an injection molding machine at an injection pressure of 500 kg 7 cm'' and a resin temperature of 250° C., and after cooling, the integrally molded product was taken out. The conductive fabric adhered to the curved surface of the inner surface of the molded product, and the resin penetrated into the gaps between the fabrics, so the adhesion was good.Also, the bottom surface of the inner surface of the molded product The maximum diameter, height, and number of pieces are 8 mm and 7 mm, respectively.
, four protrusions, and two protrusions of 15 mm and 4 mm were molded only from resin without any fabric-like material protruding from the surface.

Electromagnetic shielding (100Mtlz~100100O,
electric field) was 41 dB or more.

Mesh-like warp knitted fabric made of long polyester fibers (150
d/24 f (maximum diameter of mesh], Omm) was subjected to electroless plating to obtain a conductive fabric with a copper deposit of 21 g/m2 and a surface resistance of 0.42 Ω/ct. The elongation of this fabric when loaded with a width of 100 g/1 cm was 70% vertically and 45% vertically. Example 1
It was fixed in the same mold as the bottom lid of a calculator and was molded using an injection molding machine using A, BS resin (Stylac "-ABS, manufactured by Asahi Kasei Industries, Ltd.), injection pressure 400 Kg/c, m2, and resin temperature 240°C. An integrally molded product was obtained by injection under the following conditions.The conductive fabric adhered well along the inner surface of the molded product.

There were no problems with the molding of the protrusions. Electromagnetic wave/shielding property is 3
It was more than 7dB.

And t'　A by the bottom lid mold of the calculator used in Example 1.
A molded product made only of BS resin was obtained. 50% conductive paint (acrylic resin paint containing Sokel powder) is applied to the inner surface of this molded product.
It was applied to a thickness of μm. The surface resistance was 0.9 Ω/C+a, and the electromagnetic shielding property was 34 dB. On the other hand, after masking the protrusions present on the inner surface of the molded product, a conductive paint was applied to a thickness of 50 μm, and after drying, it was demasked.

The surface resistance of the conductive film of this molded product is 1.0Ω/cr
1, but the electromagnetic shielding performance was significantly reduced to 18 dB.

〔Effect of the invention〕

Since the molded product having electromagnetic shielding properties according to the present invention is configured as described above, electromagnetic shielding properties can be uniformly imparted to the entire surface even if it is a complex molded product having curved surface parts with various curvatures. In addition, an electrically insulating protrusion can be placed anywhere on the conductive surface of the molded product so as to coexist with electromagnetic shielding properties. Further, since the conductive fabric in the molded product according to the present invention is lightweight and is molded integrally with the molding raw material, there is no danger of it peeling off, and the electromagnetic shielding property is durable.

Moreover, the molded article according to the present invention has the characteristic that it can be manufactured by a simple process.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of a molded product having electromagnetic shielding properties according to the present invention. FIG. 2 is a sectional view showing the cross-sectional structure of a part of the molded product shown in FIG. 1. 1- Molded product having electromagnetic wave shielding properties, 2-- Mounting part, 3- Conductive fabric, 4- Projection part.

Claims (1)

[Claims] 1. A molded product consisting of a molding raw material made of synthetic resin or rubber-like material and a conductive fabric, which has a large number of gaps through which the molding raw material can pass through when molding the molded product. a fabric-like material is disposed along any surface of the molded article and integrally with the molding raw material, and at least one piece of fabric formed from the molding raw material is disposed on at least one surface of the molded article. A molded product that has electromagnetic shielding properties and is characterized by being provided with protrusions.