JPS58218196A - Method of producing electromagnetic wave shielding molded unit - 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 [Technical Field of the Invention] The present invention relates to a method for manufacturing an electromagnetic wave shielding molded body having a high electromagnetic wave shielding effect and suitable for cabinets of electrical equipment such as microcomputers.

Technical Background and Problems of the Invention In recent years, microcomputers have spread at a remarkable rate and are being used in an increasingly wide range of fields. There is a problem in that radio waves interfere with other radio wave devices such as televisions and various communication devices, and this problem has been widely discussed in various countries.

On the other hand, most microcomputers are portable and can be transported and installed anywhere; however, depending on the location where they are installed, microcomputers may be exposed to strong pulses such as spark discharges generated from surrounding equipment, equipment, etc. There is a risk of exposing itself.

These problems can be solved by providing an electromagnetic wave shielding effect to the J. Rukitoshichi net that surrounds the microcomputer.

However, for such cabinets, plastics are often used from the viewpoints of productivity, design, economy, lightness, etc., and the following is a method for imparting electromagnetic shielding properties to these cabinets. The method of the gods was adopted.

(1) A metallic electromagnetic shielding layer is provided on the outer surface of the plastic cabinet by plating, painting, thermal spraying, thermal bonding, etc.

(2) By thermoplastic resin mixed with conductive substances such as metal powder, carbon powder, metal foil, metal fiber, carbon fiber, etc.
Shape the cabinet.

(3) Using the resin injection method in glass fiber-reinforced plastic molding, a conductive fiber bundle or a preform obtained by preforming the same is placed in the key bit between the molds, and the key After injecting a liquid thermosetting resin mixed with a curing agent into the cavity of the bit, the thermosetting resin is cured at room temperature or by heating.

[Problems with the Background Art] However, in method (1), there is a risk that the electromagnetic wave shielding layer may peel off or fall off due to impact from dropping or thermal cycling, and the peeled pieces may If it falls onto the electrical circuit of a microcomputer, there is a problem in that it can easily lead to serious accidents such as short circuits and fires.

In addition, in the method (2), there is no fear that the conductive material will peel off or fall off, but there is a problem in that it is difficult to uniformly disperse the conductive material in the plastic and achieve a high electromagnetic wave shielding effect for the cabinet as a whole.

1, that is, the electromagnetic wave shielding effect 5E (db) is expressed by the following formula, S E = R + "A R = '50 + 10 βog (P, f) - 'A = 1
．． 7t'(f/P)'' 11゛(PB is volume resistivity (Ωcm) 1.f is frequency 1; number (Mllz), t indicates storage ([)) To enhance the electromagnetic wave shielding effect , it is necessary to lower the electrical resistance value 1 to improve electrical conductivity, but when metal powder or carbon powder is mixed into plastic using this method, the plastic wraps around these powders and becomes insulating. Therefore, it was difficult to obtain a cabinet with low electrical resistance.

Furthermore, when metal foil, metal fibers, etc. are used as conductive substances and mixed into plastic, the chances of the foils and fibers coming into contact with each other increase, resulting in a lower electrical resistance compared to the above method of mixing metal powder, etc. However, it was not possible to obtain 1 q of kitobinet with a sufficiently high electromagnetic wave shielding effect due to breakage and cutting of the foil and fibers during the plasticization and kneading process of the thermoplastic resin.

Furthermore, in method (3), there is no need to mix the conductive substance and resin in advance, so there is no risk of cutting the fibers, but it takes time for the thermosetting resin to take effect, which lengthens the molding cycle time. There was a moving point.

[Objective of the Invention] The present invention has been made to solve these problems, and an object of the present invention is to provide a manufacturing method for molding and curing a molded article with a high electromagnetic wave shielding effect in a short time using the method (3) above. be.

[Summary of the Invention 1] The method for producing an electromagnetic wave shielding molded article of the present invention is to produce a conductive fiber having a current-carrying terminal attached to the end thereof in a cavity of a mold.
After inserting the bundle or a preform formed by preforming the bundle, a liquid thermosetting resin composition is injected into the cavity, and electricity is applied to the current terminal to generate heat in the conductive fiber bundle or the preform, while the conductive fiber bundle or preform is heated. The present invention is characterized in that the thermosetting resin is integrally cured with the elastic string bundle or a preform obtained by preforming the same.

The conductive mm bundle used in the present invention or the preform formed by preforming it is metal fiber, metallized glass lI sheet,
It is a conductive fiber bundle such as a T-bon fiber as it is, a bundle of these fibers using a binder such as an acrylic resin, or a preform of the conductive fiber bundle.

In the present invention, a pair of current-carrying terminals are attached to these fiber bundles or preforms at intervals.

In the present invention, after injecting the liquid thermosetting resin, electricity is applied to the current-carrying terminal using an insulated wire connected thereto, thereby generating heat in the conductive fibers and discharging the thermosetting resin from the inside. Heat to accelerate curing.

In addition, in the present invention, in addition to such internal heating means, it is desirable to use a means for heating the mold by a conventional method. As such a heating means, a method is suitable in which a heater such as a cartridge type heater is embedded in the mold and is energized to generate heat.

Furthermore, in the present invention, a semi-cured thin film is prepared by spraying, for example, 1 spray of a liquid thermosetting resin mixed with a hardening agent and colored as necessary on at least one inner wall surface of the two-shaving mold. It is desirable to provide layers. In this case, the conductive III fibers are not exposed on the outer surface of the molded product, and a molded product with good appearance and high commercial value can be obtained. Further, according to this method, steps such as surface painting after molding can be omitted, so manufacturing efficiency can be improved and the cost of the product can be reduced.

[Embodiment 1 of the invention Examples of the present invention will be described below.

Example 1 First, a conductive fiber bundle was preformed to produce a preform by the following method.

Using a Zunawachi Brenner set preformer, the average diameter is 5
First, a 30-layer thickest part (hereinafter referred to as the part) of 0μ steel fiber was sprayed onto a preform mold while cutting it into 20-length pieces.
On top of that, glass roving R-231 (Japan μ-ko fiber)
70 parts of glass fiber (trade name) were sprayed together with a resin-based binder while cutting 20 parts of fiber to a length of 20 m, and the whole was placed in a high temperature curing furnace for preforming.

1. When spraying steel fibers, insert aluminum foil between the spray layers during the spraying process. An insulated wire was inserted over the Mifoil, and two energizing terminals connected to the insulated wire were attached to both ends of the preform.

Next, as shown in FIG.
Product name of unsaturated polyester resin manufactured by Mitsui Toatsu ■) 100
A liquid resin composition containing 1.5 parts of Permec N (trade name of Nippon Kayaku ■) as a hardening agent, 0.5 parts of a 6% solution of cobalt naphthenate as a hardening accelerator, and a colorant was added to the spray gun. The coating was sprayed to an average thickness of 0.2 mm, and the cartridge-type heater 1 was energized to raise the surface temperature of the mold 2 to about 60° C. to semi-cure the colored resin composition layer 4. Next, the conductive l11m preform 7 to which the previously manufactured current-carrying terminal 5 and insulated wire 6 were attached.
was placed on the female mold 8, both of the molds 3.8 were closed as shown in FIG. 2, and a voltage of 50 V was applied between both current-carrying terminals 5.5 to cause the preform 7 to generate heat. After 1 minute of electricity application, the surface temperature of the preform 7 reached 70° C., and the sprayed layer of the resin composition was cured in 1.5 minutes.

Next, while continuing to energize the cartridge type heater 1 and preform 7, a liquid heat mixture containing 2 parts of Permec N and 100 parts of Star R1-2410 (trade name of unsaturated polyester resin manufactured by Mitsui Toatsu) was heated. The curable resin composition 9 was injected into the cavity of the mold 2 from a nozzle at a pressure of 1 kg/c to fill it. The injected liquid resin composition 9 was completely cured after 2 minutes by the heating by the cartridge type heater 1 and the heat generated by the preform 7. After curing, the mold is opened and the molded product is taken out to reduce the average wall thickness to 3.
The main 11 vignettes of IIIN with high electromagnetic wave shielding effects were obtained.

For comparison, a cabinet was molded in exactly the same manner as in Example 1, except that the preform was not energized. It took 5 minutes for the unsaturated polyester resin injected into the cavity to harden.

Example 2 A steel fiber bundle with an average diameter of 50μ was used instead of the preform (aluminum foil was inserted between the fibers as a current-carrying terminal and fixed using a steel clip), but the procedure was exactly the same as in Example 1. A 1117 vignette was molded. By applying electricity to the steel fiber bundle, curing of the resin was completed in a short period of time, and a kitt7 vignette with high electromagnetic wave shielding effect was obtained.

[Effects of the Invention] As is clear from the above examples, according to the method of the present invention, a molded article having a high electromagnetic wave shielding effect can be manufactured in a shorter time than in the conventional method.

[Brief explanation of the drawing]

1 and 2 are cross-sectional explanatory diagrams showing the method of Example 1 of the present invention, FIG. 1 shows the state before closing the mold, and FIG. 2 shows the state before closing the mold. Closed unsaturated polyester resin 16] The state after injecting the polyester resin is shown.
; - 3...Female type□ 4...Colored resin composition layer 5,...
・・・・・・・・・Electricity terminal 6・・・・・・・・・
...Insulated wire 7...Preform 8...
・・・・・・Female type 9・・・・・・・・・Patent attorney representing liquid thermosetting resin composition Suyama Sa - 1))・ ＼ 1゜幡1

Claims (2)

[Claims] (1) After inserting a conductive fiber bundle with a current-carrying terminal attached to its end or a preform obtained by preforming the same into the key 1F bit of the mold, a liquid thermosetting resin composition is placed in the main 11 bit. While injecting a substance, the conductive fiber bundle or a preform obtained by preforming the conductive fiber bundle or the preform thereof and the thermosetting resin are integrally cured while the conductive m-fiber bundle or a preform thereof is heated by applying electricity to the current-carrying terminal. A method for producing an electromagnetic wave shielding molded article, characterized in that: (2) After providing a thin layer of liquid thermosetting resin mixed with a curing agent on the inner wall surface of the mold, a conductive fiber bundle with a current-carrying terminal attached to the end inside the -I iy pidi of the mold. A method for producing an electromagnetic wave shielding molded article according to claim 1, characterized in that a preform obtained by preforming the same is charged.