JPS5945336A - Synthetic resin molding material for shielding electromagnetic wave - Google Patents

Abstract

PURPOSE:A molding material of a synthetic resin useful as a cabinet for electronic devices, having high shielding effect on electromagnetic wave in a wide frequency band, obtained by blending a synthetic resin with nickel and carbon in a specific ratio. CONSTITUTION:100pts.wt. synthetic resin (e.g., epoxy resin, polyamide resin, etc.) is blended with 5-200pts.wt. fibrous or flaky nickel and 5-100pts.wt. fibrous or flaky carbon, to give the desired synthetic resin molding material for shielding electromagnetic wave.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for forming a cabinet for an electronic device such as a microcomputer; The present invention relates to a synthetic resin molded material O1 which has a high electromagnetic wave shielding effect and is suitable for use.

[Technical background of the invention 1 and its problems] In recent years, microcombiners have become popular, and are being used in an increasingly wide range of fields. Because it handles pulsed waves and contains many harmonic components, there is a problem that it interferes with other electronic devices such as televisions and various communication devices in the vicinity, and this problem is becoming a hot topic in many countries.

On the other hand, many microcomputers are portable and can be transported and installed anywhere; however, depending on the installation conditions, the computer may be directly exposed to strong pulsed radio waves (such as those generated by spark discharge) from surrounding equipment. circuits may be exposed, which may cause the computer to malfunction.

As a countermeasure to these problems, consider electrical circuits,
The best way is to reduce the radiation of unnecessary radio waves and make them less susceptible to external pulses, but there are limits to this, and it is best to have an electromagnetic shielding effect on the cabinet that surrounds the microcombiner or unit. It is necessary to do so. Moreover, such a giraffe.

Vignettes are often made of synthetic resin due to their ease of mass production, freedom of design, economy, and light weight, and many measures have been taken to improve their electromagnetic shielding properties. ing.

These measures include: (1) Provide a conductive electromagnetic shielding layer on the inner and outer surfaces 6 of the synthetic resin cabinet by plating, painting, thermal spraying, foil adhesion, or other methods.

(2) A material having an electromagnetic shielding effect, such as a wire mesh or metal foil, is placed in a molding mold in advance, and then integrated by a synthetic resin molding operation to obtain an electromagnetic shielding cabinet.

(3) Metal powder, carbon powder, metal foil, metal fiber.

An electromagnetic wave shielding gear vignette is obtained by molding a synthetic resin mixed with a conductive substance such as carbon.

Among the methods of Kotori et al., method (1) has the risk of the electromagnetic wave shielding layer on the surface peeling off and falling off due to drop impact, changes over time, heat shock, scratches, etc. If it falls onto an electric circuit, there is a problem that it may lead to accidents such as short circuit or fire.

In addition, with method (2), there is a problem that the layer such as the wire mesh may move, deform, or break due to the flow of the plasticized synthetic resin during the molding process.

Although method (3) has no fatal drawbacks, it is not easy to uniformly mix the conductive material into the synthetic resin and provide a cabinet with a sufficient electromagnetic shielding effect.

In order to enhance the electromagnetic shielding effect, K needs to improve its conductivity, but if metal powder or carbon powder is simply mixed with synthetic resin, the synthetic resin will wrap around these powders and insulate them. Therefore, it is difficult to improve conductivity. Even if 300 parts by weight of metal powder is mixed into 100,000 parts of resin, the electromagnetic wave shielding effect of such powder is still insufficient, and if the amount of powder mixed in is increased in an attempt to improve the effect, it will not be possible to form the molding material. In addition to deteriorating properties, the mechanical strength of the molded product also decreases, making it impractical.

Therefore, recently, much research has been conducted on conductive materials in the form of fibers, flakes, solid spheres, and hollow spheres, which can easily produce electromagnetic wave shielding effects even in smaller amounts than powders. These materials are metals such as copper and aluminum, and carbon.

Often made of metallized glass fiber. However, fibers, flakes, solid spheres, and hollow spheres have the same drawbacks that cause a total decrease in moldability as a molding material Fl, so the amount of the mixture must be small.

[Purpose of the invention]

It is an object of the present invention to solve the above-mentioned drawbacks, and to provide a synthetic resin molding material that has a good electromagnetic wave shielding effect over a wide frequency band.

[Summary of the invention]

In order to achieve the above object, the present inventors conducted intensive research and found that by combining nickel and carbon, a synthetic resin molding material with a relatively small amount mixed in and a high electromagnetic wave shielding effect over a wide frequency band was obtained. I found out that it can be done.

That is, in the molding step At1 consisting of a synthetic resin as a matrix, nickel, and carbon, 5 to 200 parts by weight of nickel and 5 to 100 parts by weight of carbon are blended with 100 parts by weight of the synthetic resin. This is an electromagnetic wave shielding synthetic resin molding material characterized by the following.

The synthetic resin that has a 1v advantage in the present invention is epoxy resin.

Thermosetting resins such as unsaturated polyester resins, phenolic resins, and botanical imide resins, and thermoplastic resins such as polyamide resins, polyvinyl resins, polyethylene resins, and Al3S resins are used.

The nickel used in the present invention may be in the form of fibers, solid spheres, flakes, or hollow spheres, and carbon whose surface is coated with nickel may also be used.

Further, the carbon used in the present invention may be fibrous, solid spherical,
It may have any shape such as flake or hollow sphere shape, and nickel surface coated with carbon TJU can also be used. The mixing ratio of synthetic resin, nickel, and carbon is 5 to 200 parts by weight of nickel and 5 to 100 parts by weight of resin.
~100 parts by weight of carbon is preferred. When the amount of nickel and carbon is less than 5 parts by weight each, the electromagnetic wave shielding effect is significantly reduced, and when the amount of nickel and carbon exceeds 200 parts by weight and 100 parts by weight, the electromagnetic wave shielding effect decreases. However, the fluidity as a molding material decreases, and nickel and carbon combine with each other to form lumps, resulting in a decrease in workability and moldability, which is undesirable. Therefore, it is limited to the above range.

Next, a method for measuring the electromagnetic wave shielding effect will be explained. Switching (ON-OFF operations) is constantly performed inside electronic devices. In this case, if the voltage is large, many electric field waves will be emitted, and if the current is large, many magnetic field waves will be emitted. Radio waves (electromagnetic waves that propagate through the air as a single Q) Therefore, when attempting to provide an electromagnetic wave shielding effect to the source of interference radio waves, it is necessary to measure the shielding effect on electric field waves and magnetic field waves VC.

As shown in Figure 1 A and B, the height is approximately 400 mm and the width is 20 mm.
There is a shield box 1 in the shape of an AI box with a height of 0 mm and a height of 200 mm, open at both ends 2.2', and having bottoms 4 and 4' for supporting a sample 6 on the central wall surface. Test f-1 in the center of the box
A pair of antennas, 5 for transmitting and 6 for receiving, are prepared at an interval of IQ 71 m at symmetrical positions on the sample. The transmitting antenna is connected to signal generator X, and the other receiving antenna is connected to spectrum analyzer Y.
is connected to display the attenuation rate. The electric field wave antenna is a thin wire with a length of 1QWW, while the magnetic field wave antenna is a loop-shaped antenna with 10 wires in one row.

At a certain transmission frequency (O ~ 1000M] iZ), the receiving side electric field strength Eo (V/IT+) when there is no sample,
Reception 011j electric field strength El (V/n
1) Measure 1,1 and measure the shielding effect in terms of attenuation rate (dB).

It is shown that the larger the attenuation rate, the higher the Nund effect.

[Embodiments of the invention]

Examples of the present invention will be described below.

Comparative Example 1 Carbon fiber CPAN system length 3-5 questions, aspect ratio 1
00) 20 parts by weight and ABS resin [Denka ABSCL
-301: Denki Kagaku Kogyo Co., Ltd.]1100 weight was kneaded to obtain a synthetic resin molding material $-1. For each molding month, a plate was molded and cut using a J-shaped injection molding machine, and a test J1 was obtained and evaluated using the measuring device shown in FIG. 500M) -1z electromagnetic wave shielding effect is 10.5 dB, magnetic wave shielding effect is 3 dB
Met. The results are shown in Figure 2.

Comparative Example 2 Nickel fiber (length 4-5 mm, aspect ratio 50) 50
A molding material was obtained by kneading 1,100 parts by weight of ABS resin [Tenryoku ABS CL-301: Denki Kagaku Kogyo Co., Ltd.]. All of the obtained molding materials were tested in the same manner as in Comparative Example 1, and the electromagnetic wave shielding effect and magnetic field wave shielding effect at 500 MHz were 50 dB and 60 dB, respectively. The results are shown in FIG.

Example 1 20 parts by weight of carbon fiber (PAN type, length 3 to 5 mm, aspect ratio 100), 50 parts by weight of 1ff nickel fiber (length 4 to 577 m, aspect ratio 50), and ABS resin [Denka ABS CL301: Electrochemical Kogyo Co., Ltd.] was thoroughly mixed to obtain molded silicone material. Using the thus obtained molded sheet, a plate was molded using a small injection molding machine and cut to obtain a test piece. 500mm7. The electromagnetic wave shielding effect was 62 dB, and the magnetic wave shielding effect was 168 dB. The results are shown in curve 8 in FIG.

Example 2 Nickel coated carbon fiber (PAN type length 3-5 mm
, aspect ratio 100) 70 parts by weight (including 20 parts by weight of carbon, 50 parts by weight of nickel) and A, BS resin [
Denka ABS CL301: Denki Kagaku Kogyo Co., Ltd. 10
0? (j.

We attempted to form a molded material by uniformly intermixing the wires in the placement part. Using the obtained molding material, a plate was molded and cut using a small injection molding machine to obtain a test piece. The electromagnetic wave shielding effect at this 500 Ml-1z was 60 dB, and the magnetic wave shielding effect was 66 dB. The results are shown in curve 5 in FIG.

〔Effect of the invention〕

According to the present invention, a synthetic resin molding material having an excellent electromagnetic wave shielding effect in a wide frequency band can be obtained by blending a synthetic resin, nickel, and carbon in a predetermined ratio.

[Brief explanation of the drawing]

Figure 1 (A) is a cross-sectional view showing a device for measuring the electromagnetic wave shielding effect, Figure 1 (B) is the perspective view of the device shown in Figure 1, and Figures 2 and 6 are the electromagnetic wave shielding of conventional molding materials. FIG. 4 is a graph showing the electromagnetic wave shielding effect according to the month of molding of the present invention. 1... Shield box, 6... Sample, 4.4'.
... Groove, 5... Transmitting antenna, 6... Receiving antenna, X... Signal generator, Y... Spectrum analyzer. Patent Applicant Toshiba Kumical Co., Ltd. Agent Patent Attorney Eiji Morota 1 Figure ↓ Old 1 5 3 6 Hiromaki Hiromaki (MHzJ 2nd frequency (MH2) 2nd frequency (Ml-1z) 2 Figure J @ (MHz) 3 Figure circumference frequency (MHz) Figure 4 frequency (Mf-1z)

Claims (1)

[Claims] A molding material consisting of a synthetic resin, nickel, and carbon, which becomes the IU material, is used in the above synthesis (☆ 5 to 200 parts by weight of nickel and 5 to 100 parts by weight of carbon per 1 part of 100'l of fat). An electromagnetic wave shielding synthetic resin molding material that is characterized by being formulated with: