JPS58168300A - Electromagnetic shielded molded part - 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 The present invention relates to tS shield molded products, which have been developed in recent years by IC,
With the rapid development of electronics technology represented by LSI, digital electronic devices such as computers, electronic games, video games, electronic cash registers, switching power supplies, tental clocks, IT desks, word processors, etc. that use ICs and LSIs are increasing. It has become widely used. At the same time, plastic housings can be mass-produced as housings for digital electronic devices, and their moldability and
It has become widely used due to its excellent workability and good electrical insulation properties.

On the other hand, digital electronic devices generate more than 10,000 pulses per second, and these electromagnetic waves are radiated into space. The electromagnetic wave energy emitted from such digital electronic devices can cause problems such as noise and image disturbance (so-called electromagnetic interference) on radios, televisions, and wireless communication equipment.

Therefore, while the plastic housing has the above-mentioned advantages, it is transparent to electromagnetic energy, so it is necessary to shield interference radio waves in this area.
An electromagnetic shield, armor, etc. will be required. For this reason, conductive plastics containing carbon or metal have already been researched, but this method requires adding a large amount of conductive filler to the plastic, and unless it is mixed uniformly, good conductivity and electromagnetic shielding vehicles cannot be obtained. I can't do it. Further, even if the conductive filler is mixed uniformly, the filler is exposed on the surface, resulting in poor appearance, reduced strength, and impaired electrical insulation. Further, there was a drawback that the mixed metal filler was oxidized and the electromagnetic shielding properties were deteriorated.

In view of the above points, the present invention solves the above problems and has excellent appearance, conductivity, electromagnetic shielding properties, and electrical insulation.

We provide electromagnetic shielding molded products with excellent properties.
After a thermoplastic resin film or sort is attached to the mold cavity surface, a thermoplastic resin mixed with a conductive filler is injection molded, and the outside of the thermoplastic resin molded body mixed with a conductive filler is formed. This can be effectively achieved by using an electromagnetic shielding molded product formed by integrally fusing a thermoplastic resin layer to the surface.

The present invention will be explained in detail below.

The thermoplastic resin used in the present invention is a thermoplastic resin such as polyvinyl chloride, polyamide, ABS, polystyrene, polyphenylene oxide, polypropylene, polyethylene, or polycarbonate. Preferably, heat to mix the conductive filler is suitable for injection molding, suitable for mixing the conductive filler, suitable for film or sheet processing, and good compatibility between the molded product and the film or sheet. The following combinations of the plastic resin and the thermoplastic resin of the film or sheet are preferred.

Polystyrene-polystyrene/polyphenylene oxide, ABS-ABS/polycarbonate/polyvinyl chloride, polyamide-polyamide.

Polycarbonate - ABS/polycarbonate.

Polypropylene-polyethylene/polypropylene, polyphenylene oxide-polypropylene/polystyrene, polyvinyl chloride-ABS/polymethyl methacrylate/polyvinyl chloride.

The conductive fillers used in the present invention include graphite, conductive carbon black, silver/copper/nickel/stainless steel powder, aluminum flakes, stainless steel flakes, nickel flakes, carbon fibers, aluminum ribbons, and aluminum fibers M.

It can be appropriately selected from aluminum coated glass fiber and the like. Only one kind of conductive filler may be added to the thermoplastic resin, or several kinds may be appropriately mixed and used. Further, the amount of the conductive filler added to the thermoplastic resin varies depending on the type of thermoplastic resin, the type of conductive filler, and the combination thereof, and can be appropriately selected depending on the purpose. However, from the viewpoint of flowability and miscibility, the desirable shape of the conductive filler is a flake with a thickness of Q, lya or less and a large surface area of 4 or less, or a diameter (D) of 10-100 μm and a length of L). Fine fibers with a length of 1 to 411 m are desirable, and the ratio of the thermoplastic resin to the conductive filler is determined by the electromagnetic shielding properties and flowability, and the volume ratio of the conductive filler is 10 to 2.
5% is desirable. When the volume ratio is less than 10%, sufficient electromagnetic shielding properties cannot be obtained, and when it is larger than 25%, the amount of conductive filler becomes large, resulting in poor flow and difficulty in uniformly distributing the conductive filler. Typical formulation examples are shown below.

Example of formulation (the subtitles indicate the percentage of conductive filler in Shinkaku, and ms indicates the percentage of volume of porcelain resin in %) Next, the present invention will be explained with reference to the drawings. FIG. 1 is a partial plan view of the injection molding apparatus. 11
12 is a fixed die plate of the injection molding machine, 12 is a movable die plate of the injection molding machine, 13 is a tie bar, 14 is a fixed mold, 15 is a movable mold, 16 is a thermoplastic resin film or sheet, and 17 is a heating device. , 18 is a pachyme device. FIG. 2 is a sectional view showing an example of a molded product. 20
2 is a molded product, 21 is a molded product mixed with a conductive filler, 22 is a coating formed of a thermoplastic resin film or sheet, and 23 is a conductive filler.

Therefore, a conductive filler is added to the thermoplastic resin according to the above-mentioned formulation example, and the mixture is kneaded using an extruder to produce a uniform composite. Injection molding is performed using this compound. That is, this compound is placed in advance into the hopper of an injection molding machine and plasticized and melted within the cylinder. On the other hand, as shown in FIG. 1, the thermoplastic resin film or sheet 16 is held by a known feeding device (not shown) and a winding device (not shown).
It is located between the fixed side mold 14 and the movable side 15. (
The film or sheet may be held in either the horizontal or horizontal direction or the vertical or vertical direction. )The feeding device and the winding device are linked to the injection molding machine, and feed out the film or sheet intermittently according to the molding cycle.
vinegar. Therefore, the thermoplastic resin film or sheet
When the mold of the injection molding machine is opened, it is sent out between the stationary mold and the movable mold by the delivery device and the winding device. The thermoplastic resin film or sheet sent out is then clamped between the parting surfaces of the stationary mold and the movable mold by the mold clamping operation of the injection molding machine. Note that it is desirable that a thick sheet be preheated by the heating device 17.

Next, the film or sheet is vacuum-suctioned by a vacuum device 18 connected to the cavity mold.
Adsorbs to the mold cavity surface. The plasticized and molten compound is then injected into the mold, and after cooling, the molded product is
After cutting the outer peripheral seam of the molded product using a Thomson blade (installed in advance in the mold) that moves in conjunction with a known air cylinder or hydraulic cylinder, the mold is opened and removed from the mold. As shown in FIG. 2, an electromagnetic shield molded product whose surface is covered with a thermoplastic resin film or sheet is obtained.

Although the above description has been made based on examples, it is also possible to perform injection molding by, for example, using a known injection molding method or by inserting a vacuum-formed sheet in advance into a mold.

The electromagnetic shield molded product thus obtained has an excellent appearance and
It has electromagnetic shielding properties and excellent electrical insulation properties.

Therefore, even if an electrical leakage accident occurs, there will be no electric shock, and the trouble of painting can be saved. Additionally, it can be produced using a conventional injection molding machine, requiring less capital investment. Furthermore, it can be mass produced and can be provided at low cost due to cost reduction, which has great economic and practical value□.

Example 1 A polystyrene sheet with a thickness of 0.5 mm is sandwiched between the notching surfaces of a stationary mold and a movable mold by far-infrared stitching.

Next, the valve of the piping connected to the vacuum pump is opened and vacuum suction is applied to adsorb the sheet to the mold cavity surface, thereby forming the sheet.

Immediately after forming the sheet, a compound containing a conductive filler was injection molded to obtain a box-shaped molded product having dimensions of 200 x 150 x 40D and a thickness of 365M.

The compound in this case is 75% by volume polystyrene (volume is omitted below), 3% carbon black, 18% aluminum flakes, and 4% aluminum fibers, mixed in a single-screw extruder, extruded, and cut into pellets. It was used.

Injection molding conditions are mold temperature 60℃, injection pressure 1,000s
t/d, molding temperature 210°C, and injection time 2 seconds.

The molded product obtained had a thin layer of polystyrene alone on the outer surface and a thick layer of polystyrene containing a conductive filler on the inner surface, and exhibited good surface properties and excellent surface insulation. Ta.

Also, regarding the electromagnetic shielding characteristics, W, D, Na5OnH
! When measured according to the ISO method, it showed a shielding property of 40 dB at 1000 MN, and there was no risk of electromagnetic interference even when used as a plastic housing for a digital electronic device.

The boundary between the polystyrene single layer and the conductive filler-containing polystyrene layer was fused during injection molding, so there was no problem with strength.

Example 2 A sheet of ABS resin with a thickness of Q and 53111 was used for the outer surface, and a compound of 85% ABS resin, 1396 aluminum flakes, and 2% aluminum fiber was used for the inner surface, the same as in Example 1. Molded using a mold.

The injection molding conditions were a mold temperature of 70° C., an injection pressure of 1,200, a */ds molding temperature of 230° C., and an injection time of 1.5 seconds.

The obtained molded product had excellent surface properties, surface insulation properties, and shielding properties.

[Brief explanation of drawings]

Fig. 1 is a plan view of the injection molding apparatus, and Fig. 2 is a sectional view of the molded product. Thermoplastic resin film or sheet 1
7...Heating device 18...Vacuum device Patent applicant: Aron Kasei Co., Ltd. Agent Masaaki Ono l Group procedural amendment (spontaneous) 1. Indication of the case 1988 Patent, Application No. 051 ! 14 No. 2, Title of the invention Electromagnetic seal: Molded product 3, Relationship with the case of the person making the amendment Patent applicant address 1-14-1 Nishi-Shinbashi, Minato-ku, Tokyo
Name (050) Aron Kasei Co., Ltd. Representative 'Sakatabe Eguchi 4, Agent 5, Date of amendment order Voluntary 6, Number of inventions increased by amendment 10 Subject of amendment (1) Name of invention in application Column (2) Full text of the specification 8, Contents of amendment (2) The full text of the specification is corrected as shown in the attached sheet. Description 10 Name of the invention Method for manufacturing electromagnetic shielding molded product 2, Claims By attaching a thermoplastic resin film or sheet to the surface of a cavity, and then injection molding a thermoplastic resin mixed with a conductive filler. A method for producing an electromagnetic shielding molded product, which comprises integrally fusing a thermoplastic resin layer to the outer surface of a thermoplastic resin molded product mixed with a conductive filler. 3. Detailed Description of the Invention The present invention relates to a method for manufacturing an electromagnetic shield molded product. In recent years, electronics represented by IC, LSI, 1
With the rapid development of smartphone technology, combination machines, computers, electronic games, video games, electronic cash registers, switching power supplies, digital clocks, molds, and
Digital electronic devices such as word processors have become widely used. At the same time, plastic housings have come to be widely used as housings for digital electronic devices because they can be mass-produced, have excellent moldability and processability, and have good electrical performance. On the other hand, digital electronic devices generate more than to, ooo pulses every second, and these electromagnetic waves are radiated into space. Electromagnetic wave energy radiated from such digital electronic devices may cause problems such as noise and image disturbance (so-called electromagnetic interference) in radios, televisions, and wireless communication devices. Therefore, while the plastic housing has the above-mentioned advantages, it is transparent to electromagnetic energy, so it is necessary to shield interference radio waves in this area.
・ Electromagnetic shielding will be required. For this reason, conductive plastics containing carbon or metal are already being researched, but this method is
Good conductivity and electromagnetic shielding effects cannot be obtained unless a large amount of conductive filler is added to plastic and mixed uniformly. Furthermore, even if the conductive filler is mixed uniformly, the filler is exposed on the surface, resulting in disadvantages such as poor appearance, reduced strength, and impaired electrical continuity. Further, there was a drawback that the mixed metal filler was oxidized and the electromagnetic shielding properties were deteriorated. In view of the above points, the present invention solves the above problems and provides an electromagnetic shield molded product that has excellent appearance, conductivity, electromagnetic shielding properties, and electrical insulation properties. Then, a thermoplastic resin film or sheet is attached to the mold cavity surface by injection molding a thermoplastic resin mixed with a conductive filler. This can be effectively achieved by a method for producing an electromagnetic shielding molded product, which is characterized by integrally fusing a thermoplastic resin layer to the outer surface of a thermoplastic resin molded product mixed with a conductive filler. The present invention will be explained in detail below. The thermoplastic resin used in the present invention is a thermoplastic resin such as polyvinyl chloride, polyamide, ABS, polystyrene, polyphenylene oxide, polypropylene, polyethylene, or polycarbonate. Preferably, a conductive filler is mixed because it is suitable for injection molding, suitable for mixing with a conductive filler, suitable for processing a film or sheet, and has good compatibility between the molded product and the film or sheet. Thermoplastic resin and film or/-
The following combinations of thermoplastic resins are preferred. Polystyrene□Polystyrene/polyphenylene oxide, ABS ABS, polycarbonate/polyvinyl chloride, polyamide□Polyamide/polycarbonate
ABS-, t'recarbonate. Polypropylene □ Polyethylene/polypropylene, polyphenylene oxide □ Polypropylene/polystyrene, polyvinyl chloride □ ABS/polymethyl methacrylate/polyvinyl chloride. The conductive filler used in the present invention is graphite, conductive carbon black, silver/copper/nickel/stainless steel powder, aluminum flake, stainless steel flake, nickel flake, carbon fiber, aluminum ribbon, aluminum fiber. Aluminum coated glass fin. The conductive filler can be appropriately selected and used from the above-mentioned thermoplastic resin. Only one type of conductive filler may be added to the thermoplastic resin, or several types may be appropriately mixed and used). The amount of the conductive filler added to the resin can be appropriately selected depending on the type of thermoplastic resin or the type of conductive filler and the combination thereof, depending on the strength and application. From the viewpoint of miscibility, the desirable shape of the conductive filler is a flake with a thickness of 0.1 fi or less and a large surface area force of 4 or less, or a diameter of 10 to 100 mm.
Fine fibers with a length L) of 1 to 4 cm are desirable. Furthermore, the ratio of the thermoplastic resin to the conductive filler is determined by the electromagnetic shielding properties and the tendency to break up.The volume ratio of the conductive filler is 10.
~25% is desirable. When the volume ratio is less than 10%, sufficient electromagnetic shielding properties cannot be obtained, and when it is larger than 25%, the amount of conductive filler increases, resulting in poor flow and difficulty in uniformly distributing the conductive filler. Typical formulation examples are shown below. Formulation Example Next, the present invention will be explained with reference to the drawings. FIG. 1 is a partial plan view of the injection molding apparatus. 11 is a fixed die plate of the injection molding machine, 12 is a movable die plate of the injection molding machine, 13 is a tie bar, 14 is a fixed mold, 15 is a movable mold, 16
1 is a thermoplastic resin film or sheet, 17 is a heating device, and 18 is a Pakim device. FIG. 2 is a sectional view showing an example of a molded product. 20 is a molded product, 21 is a plastic resin molded body mixed with a conductive filler, 22 is a coating formed of a thermoplastic resin film or sheet, and 23 is a conductive filler. Therefore, a conductive filler is added to the thermoplastic resin according to the above-mentioned formulation example, and the mixture is kneaded using an extruder to produce a uniform powder. Injection molding is performed using this compound. That is, this compound is placed in advance into the hopper of an injection molding machine and plasticized and melted within the cylinder. On the other hand, as shown in FIG. 1, the thermoplastic resin film or sheet 16 is held by a known feeding device (not shown) and a winding device (not shown).
It is located between the fixed side mold 14 and the movable side 15. (
The film or sheet may be held in either the horizontal or horizontal direction or the vertical or vertical direction. ) The feeding device and the winding device are interlocked with the injection molding machine, and feed out the film or sheet intermittently in accordance with the molding cycle. Therefore, the thermoplastic resin film or sheet is delivered between the stationary mold and the movable mold by the delivery device and the winding device when the mold of the injection molding machine is opened. The thermoplastic resin film or sheet sent out is then clamped between the barging surfaces of the stationary mold and the movable mold by the mold clamping operation of the injection molding machine. Preferably, the film or sheet is preheated by a device 17. Next, the film or sheet is vacuum-suctioned by a Paquim device 18 connected to the mold, and adsorbed to the mold cavity surface.Then, the plasticized and molten compound is transferred to the mold. After being injected into the mold and cooled, the molded product is cut by a Thomson blade (installed in advance in the mold) that moves in conjunction with a known air cylinder or hydraulic cylinder. The mold is opened and taken out from the mold.As shown in FIG. 2, an electromagnetic shield molded product whose surface is covered with a thermoplastic resin film or sheet is obtained. In the known painted injection molding method, a pre-vacuum formed sheet can be inserted into the mold and then injection molded - the electromagnetic molded product thus obtained has an excellent appearance,
It has electromagnetic shielding properties and excellent electrical insulation properties. Therefore, even if an electrical leakage accident occurs, there will be no electric shock, and the trouble of painting can be saved. In addition, it can be produced using a high-quality injection molding machine, requiring less capital investment. Furthermore, it can be mass-produced and can be provided at low cost due to cost reduction, which has great economic and practical value. Example 1 A 0.5-thick polystyrene sheet is softened by heating with a far-infrared lamp. After this sheet is set in the movable mold shown in FIG. 1, it is held between the parting surfaces of the stationary mold and the movable mold by the mold clamping operation of the injection molding machine. Next, the valve of the piping connected to the vacuum pump is opened and vacuum suction is applied to adsorb the sheet to the mold cavity surface, thereby forming the sheet. Immediately after forming the sheet, a compound containing a conductive filler is injection molded to form a 200x150x40m-
, 111 and a thickness t of 3.5 mm was obtained. The compound in this case is 75% by volume polystyrene (volume is omitted below), 3% carbon black, 18% aluminum flakes, and 4% aluminum fibers, mixed in a single-screw extruder, extruded, and cut into pellets. It was used. The injection molding conditions were a mold temperature of 60°C and an injection pressure of t,oo. kg/cIA, molding temperature 210°C, injection time 2 seconds. The molded product obtained had a thin layer of polystyrene alone on the outer surface and a thick layer of polystyrene containing a conductive filler on the inner surface, and exhibited good surface properties and excellent surface insulation. Ta. In addition, regarding the electromagnetic shielding characteristics, when measured according to the method of W, D, Na5on, etc., it is 100 MI (40 d at z)
It exhibited a shielding property of B, and there was no risk of electromagnetic interference even when used as a plastic housing for digital electronic equipment. The boundary between the polystyrene single layer and the conductive filler-containing polystyrene layer was fused during injection molding, so there was no problem with strength. Example 2 A sheet of ABS resin with a thickness of 0.51 was used for the outer surface,
The inner surface is made of 85% ABS resin and 13% aluminum flakes.
% and 2% aluminum fibers were used and molded using the same mold as in Example 1. Injection molding conditions are mold temperature 70℃, injection pressure 1,200℃.
Moan/-1 The molding temperature was 230°C and the injection time was 1.5 seconds. The obtained molded product had excellent surface properties, surface insulation 1, and shielding properties. 4. Brief description of the drawings FIG. 1 is a plan view of the injection molding apparatus, and FIG. 2 is a sectional view of the molded product. 14... Fixed side mold 15... Movable side mold 16... Thermoplastic resin film or sheet 17... Heating device 18...・Paki, -mu device

Claims (1)

[Claims] After a thermoplastic resin film or sheet is attached to the mold cavity surface, a thermoplastic resin mixed with a conductive filler is injection molded, and a thermoplastic resin molded body mixed with a conductive filler is injected onto the outer surface of the thermoplastic resin molded body. An electromagnetic shield molded product made by fusing resin layers together.