JPH0866936A - Manufacture of resin molded body for electromagnetic wave shield or magnetic shield - Google Patents

Abstract

PURPOSE: To obtain a resin molded body for electromagnetic wave shield or magnetic shield which is effective for protecting an electronic apparatus from influence of external electromagnetic wave by integrating a resin layer having a shielding function with a resin layer having no shielding function as a multilayer structure. CONSTITUTION: A shield resin layer cavity 21 and a non-shield resin layer cavity 22 are provided in a mold on one face. The cavities 21 and 22 are arranged symmetrically by 180 deg. with center at a pivot 23. At first, a shield resin layer (thickness of t1 ) 25 is molded by a first injection unit 24. After mold opening, it is turned for 180 deg. in a state that the molded shield resin layer 25 is attached to the mold so as to move it to the position of the non-shield resin layer cavity 22, a non-shield resin layer is jetted, and injection is performed after mold opening. At this time, a mold rotating device is generally attached to a movable platen of a molding machine.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a personal computer, a word processor,
Protects magnetic field control electronic parts such as electromagnetic wave shielding resin moldings or vehicle speed control hall elements that are useful for protecting electronic devices such as cellular phones, cordless phones, and personal handy phones from the effects of external electromagnetic waves. The present invention relates to a method for producing a resin molded body for magnetic shield useful for manufacturing.

[0002]

2. Description of the Related Art For electromagnetic wave shielding resin moldings, a method has been generalized in which one surface of an insulating resin molding, for example, an inner surface of an outer box, is made conductive. Examples of the conductive treatment method include a method of spraying a metal such as Zn on the inner surface of the outer box, a method of applying a conductive resin coating material containing Ag powder, Cu powder, Ni powder, etc., and a metal foil such as Al foil. Generally, a method of laminating, a method of electroplating or vacuum depositing a metal such as Cu, etc. are adopted, but since these methods have a plurality of manufacturing steps and become expensive, brass fiber, Al fiber, Al flakes, stainless fiber,
A method of molding with a conductive resin in which a conductive filler such as carbon fiber is kneaded has been adopted. However, in this conductive resin molded body, the color of the molded body is limited by coloring with the conductive filler, because the conductive filler is raised on the surface, the smoothness of the molded body surface cannot be maintained, and There is a problem such as pain when touching the protrusions. Therefore, as shown in FIG. 3, a conductive resin molded body 31 whose surface is covered with a resin layer 32 containing no conductive filler has been demanded.

On the other hand, as a magnetic shield material, permalloy (N
i-Fe alloy), electromagnetic soft iron (pure iron, low carbon steel, Armco iron), silicon steel (Fe-Si alloy), amorphous alloy (Co-Fe alloy, Fe-Si-B alloy), etc. Cutting and press processing are mainly used, but recently, resinization of this magnetic shield material has been actively studied. This is the soft magnetic metal powdered, kneaded into resin (including rubber, thermoplastic elastomer, etc.) and molded using general-purpose plastic molding technology. Compared to cutting / pressing products of metal materials Thus, there are advantages that the degree of freedom of the product shape can be expanded and that the molding cycle can be increased, so that the cost can be reduced. However, on the other hand, the use of resin for the magnetic shield material has the following disadvantages. That is,
The ability to shield a DC magnetic field is required to have a high magnetic permeability. However, if a soft magnetic metal is pulverized, the magnetic permeability will be greatly reduced. However, the magnetic permeability of the resin molding itself cannot be made larger than the magnetic permeability of the powder itself. The magnetic permeability represents the easiness of magnetization, that is, the ease of passing a magnetic flux, and is the most important value for a soft magnetic material. It is important that the magnetic permeability has a maximum magnetic permeability and an initial magnetic permeability. The maximum permeability of soft magnetic metal used for magnetic shield material is pure iron: 8,000
0, Silicon steel plate: 30,000, Permalloy: 25,000 ~ 150,00
It is 0 mag. To give an example of this change in maximum permeability,
In the case of cutting and pressing of metal materials, the product of 16,000 (-) becomes 4,500 (-) in the powder sintered product, and further decreases to about 300 (-) in the resin molded product.

As a method for compensating for the decrease in magnetic permeability, that is, the decrease in magnetic shield performance, a method of forming multiple layers by sandwiching layers having no magnetic shield effect can be considered. This will be described by taking the shield case 41 having the shape shown in FIG. 4 as an example.
It is known that the magnetic shielding effect is larger and the economical advantage is obtained when the weight is triple or triple. The inner cylinder 42 has a plate thickness t.
₆ , the outer diameter r ₁ , the outer cylinder 43 has a plate thickness t ₇ , the outer diameter r ₂ , the magnetic shield effect of the double infinite cylindrical structure S
(= H ₁ / H ₀ ), where S ₁ is the magnetic shield effect of the inner cylinder 42 alone and S ₂ is the magnetic shield effect of the outer cylinder 43 alone, S = [1 + S ₁ + S ₂ + S ₁ · S ₂ {1- (R ₁
/ R ₂ ) ² }]. Incidentally, the calculation formula of the magnetic shield effect S of a single infinite cylinder (not shown) having a magnetic permeability μ, a plate thickness t, and an outer diameter r is expressed by S = 1 + 0.5 · μ · t / r. The improvement of the magnetic shield performance due to such multilayering is achieved by cutting the first metal shield layer (such as the inner cylinder 42) and the outer cylinder 43 (in the outer cylinder 43) in the case of cutting / pressing a metal material.
It is common to provide a space between the first magnetic shield layer and the second magnetic shield layer, but in the case of resin, a soft magnetic field is provided between the first magnetic shield layer and the second magnetic shield layer. It is conceivable to provide the insulating resin layer 44 containing no filler.

[0005]

Hereinafter, a resin layer containing a conductive filler or a soft magnetic filler and having an electromagnetic wave shielding function or a magnetic shielding function is a shield resin layer, and a resin layer not containing these fillers is a non-shielding resin. Define as a layer. Generally, resin moldings for electromagnetic wave shielding
As shown in FIG. 5A, 51 is composed of two layers, a shield resin layer 52 and a non-shield resin layer 53, and the magnetic shield resin molding 54 is a first shield resin layer as shown in FIG. 5B. 52
a, unshielded resin layer 53 and second shielded resin layer 52
It is composed of three layers b. As a method for forming the shield resin layer 52 and the non-shield resin layer 53 in multiple layers, the method shown in FIG.
In the case of the two-layer structure as shown in (a), the preformed shield resin layer 52 and the non-shield resin layer 53 are joined by fitting or bonding. Prepare two types of molds, first mold the shield resin layer 52 with the first mold, and then mold this with the second mold.
And the unshielded resin layer 53 is integrally molded. There is a method of forming a non-shielding resin layer 53 by applying a non-shielding resin paint to the surface of the pre-molded shielding resin layer 52. Note that the method can also reverse this order arbitrarily.

On the other hand, in the case of the three-layer structure as shown in FIG. 5B, the first shield resin layer 52a, the non-shield resin layer 53 and the second shield resin layer 52b which have been formed in advance are fitted in this order. Match or glue and bond. The first shield resin layer 52a and the second shield resin layer 52b, which are molded in advance, are fitted and adhered via the adhesive layer 53 of the non-shield resin. Prepare three types of molds, first mold the first shield resin layer 52a with the first mold, and then set the first shield resin layer 52a in the second mold to form the non-shield resin layer. 53 is integrally molded. Next, there is a method of setting the two-color molded product in a third mold and integrally molding the second shield resin layer 52b therein. However, since these methods require a plurality of molds, the mold cost becomes high. Since a plurality of resin molding steps and secondary processing steps such as fitting, bonding and coating are required, the manufacturing cost increases, resulting in a high product cost. Therefore, an object of the present invention is to provide a method for inexpensively manufacturing a resin molding for electromagnetic waves or magnetic shields by a simple process and a single process.

[0007]

A method of manufacturing a resin molding for electromagnetic waves or magnetic shields according to the present invention comprises a resin layer having a shielding function and a resin layer having no shielding function.
It is characterized in that the resin is integrated as a multilayer structure of both resin layers by a color or three-color injection molding machine.

Hereinafter, the present invention will be described in detail with reference to the drawings. 1 (a) and 1 (b) are vertical cross-sectional views showing an example of an electromagnetic wave shielding resin molded body and a magnetic shielding resin molded body obtained by the method of the present invention, respectively. As shown in FIG. 1A, the electromagnetic wave shielding resin molded body 1 generally includes a shield resin layer 2 / non-shield resin layer 3
2 layers, and the injection order is arbitrary. See also FIG.
As shown in (b), the magnetic shield resin molded body 4 generally includes a first shield resin layer 2a / non-shield resin layer 3 /
It is composed of the second shield resin layer 2b, and the injection order is this order.

The resin forming the non-shielded resin layer 3 and the base material for forming the shielded resin layer 2 are polyethylene, polypropylene, polystyrene, acrylonitrile-butadiene-styrene block copolymer, vinyl chloride resin, polyamide, polycarbonate. , Polybutylene terephthalate, modified polyphenylene ether,
Thermoplastics such as polyacetal, polyarylate, polysulfone, polyethersulfone, polyetherimide, polyphenylene sulfide, polyetheretherketone, polyamideimide, polystyrene-based thermoplastic elastomer, polyolefin-based thermoplastic elastomer, polyester-based thermoplastic elastomer, In addition to thermoplastic elastomers such as polyamide-based thermoplastic elastomers, special cross-linked rubbers prepared for injection molding such as two-component addition reaction type silicone rubbers can be mentioned.

As the filler added to the above base material to form the shield resin layer 2, brass fiber, Al fiber, Al
Flakes, stainless fiber, carbon fiber, Ag powder, Cu
Conductive fillers such as powder, Ni powder, graphite powder, carbon black, and magnetic shield fillers include Permalloy (Ni-Fe alloy) powder, electromagnetic soft iron (pure iron, low carbon steel, Armco iron) powder, silicon steel ( Fe-Si alloy) powder, amorphous alloy (Co-Fe alloy, Fe-Si-)
B alloy) soft magnetic metal powder such as powder. Kneading the filler into the resin is done with two rolls, a pressure kneader,
A general-purpose resin kneading machine such as a Banbury mixer, a single-screw kneading extruder, a twin-screw kneading extruder, a single-axis rotor kneading extruder, a two-axis rotor kneading extruder can be used. This kneaded mixture can be easily injection-molded when it is made into pellets or powder by a pelletizer or a pulverizer.

The two-color or three-color injection molding is a molding system using a rotary two-station or three-station mold by an injection molding machine having two or three injection units in one machine. There is an advantage that time is not required to move between them and cost can be saved. First,
Regarding the two-color injection molding, the shielding resin layer 2 (thickness t ₁ ) and the non-shielding resin layer 3a (thickness t ₁ ) having the same sectional shape as the electromagnetic wave shielding resin molding shown in FIG.
₂ ) The case of forming a disk consisting of and will be explained as an example. As shown in FIG. 2, a die for this purpose has a shield resin layer cavity 21 and a non-shield resin layer cavity 22 in a die on one surface.
It is located 180 ° symmetrically around 23. First, the shield resin layer (thickness t ₁ ) 25 from the primary injection unit 24
After the mold is opened, the shield resin layer 25 molded product is rotated 180 ° and moved to the position of the non-shield resin layer cavity 22 with the molded product of the shield resin layer 25 attached to the mold, and the non-shield resin layer is injected to open the mold. After that, eject. At this time, the mold rotating device is generally mounted on the movable plate side of the molding machine, and therefore the shield resin layer cavity 21 of the first injection is formed in the movable plate side mold 26 at a depth t ₁ from the parting surface. The second injection unshielded resin layer cavity 22 is formed in the fixed plate side (screw side) die 27 at a depth t ₂ from the parting surface. In this mold structure, the primary injection unit 24 is arranged vertically and injection is carried out from the mold parting surface 28, and the secondary injection unit 29 is arranged horizontally and is injected from the sprue bush of the stationary plate side mold 27. Is generally used. The molding cycle can be doubled by performing the primary injection of the next molded product simultaneously with the secondary injection.

The three-color injection molding is an application of the two-color injection molding. This also has a cross-sectional shape similar to that of the magnetic shield resin molding shown in FIG. 1B, and the first shield resin layer 2a.
An example of molding a disk composed of (thickness t ₃ ) / non-shielding resin layer 3 b (thickness t ₄ ) / second shielding resin layer 2 b (thickness t ₅ ) will be described. In this case, the molds are arranged at symmetrical positions of 120 ° around the rotation axis, and the first shield resin layer cavity is formed in the mold on the movable plate side at a depth t ₃ from the parting surface. The injection non-shielded resin layer cavity has a depth t ₄ from the parting surface to the fixed plate side mold.
The second shield resin layer cavity of the third injection is formed in the fixed plate side mold at a depth t ₄ from the parting surface.
It is formed by + t ₅ . First, the first shield resin layer is molded by the primary injection unit, and after the mold is opened, the first shield resin layer molded product is rotated 120 ° with the mold attached to the mold and moved to the non-shield resin layer cavity. After injecting the shield resin layer and opening the mold, with the integrally molded product of the first shield resin layer and the non-shield resin layer attached to the mold, further rotate 120 ° and move to the second shield resin layer cavity. , The second shield resin layer is injected, the mold is opened, and then ejected. In this three-color injection molding, the second injection of the next molded product is performed simultaneously with the third injection, and the first injection of the next molded product is performed.
Subsequent injection can also be performed, and the molding cycle can be tripled as compared with molding for each color.

[0013]

【Example】

(Example 1) Vinyl chloride resin: TK-700 (manufactured by Shin-Etsu Chemical Co., Ltd., trade name) 100 parts by weight, methyl methacrylate-butadiene-styrene copolymer (impact-strengthening agent) 7 parts by weight,
3 parts by weight of octyl tin mercaptide (stabilizer), 1.5 parts by weight of polymethylmethacrylate (fluidity modifier), 0.3 parts by weight of stearic acid (lubricant) were kneaded by a twin-screw extruder and hard chloride as an unshielded resin. A vinyl resin compound (hereinafter referred to as a PVC compound) was prepared. Next, with respect to 100 parts by weight of this PVC compound, φ15 μm x 0.15 mm long stainless steel short fiber: SMF-M
(Kawatetsu Techno Research Co., Ltd., trade name) 50 parts by weight, φ8μ
mx 6 mm long stainless steel filament: 5 parts by weight of Susmic fiber (trade name, manufactured by Tokyo Steel Co., Ltd.) is kneaded with a Banbury mixer, and the volume resistivity of the electromagnetic wave shielding resin is 0.5 Ω · cm, and the electromagnetic wave shielding property is 40 at 100MHz
A stainless fiber compound compound of 25 dB at 1 GHz was prepared.

Next, the mold clamping force is 50 tons and the maximum injection capacity is 160 gf.
The two-color injection molding machine in which the primary injection unit is arranged vertically, the secondary injection unit is arranged horizontally, and the mold rotating device is arranged on the side of the molding machine movable plate: All Rounder 270M 500-2
Shield resin layer cavity (depth 2mm × φ100mm) and unshielded resin that are placed symmetrically about the rotation axis by 180 ° in a mold on one side using 10 × 2 (trade name, manufactured by Arburg) A disk-shaped molded body (thickness: 3 mm × φ 100 mm) was injection-molded as a trial using a mold having a layer cavity (depth: 1 mm × φ 100 mm). The shield resin layer cavity is formed in the movable plate side mold at a depth of 2 mm from the parting surface, and the non-shield resin layer cavity is formed in the fixed plate side mold at a depth of 1 mm from the parting surface. The shield resin layer molded by the first injection rotates 180 ° and moves to the non-shield resin layer cavity position, then the second
Subsequent injections were performed and the molding cycle was 4 times / minute. The finished product had a thickness of 3 mm x φ100 mm, and the interface between the shield resin layer and the non-shield resin was completely adhered, and when attempting to forcibly destroy it, any position other than the interface was torn. Electromagnetic wave shield characteristics are 40 dB at 100 MHz and 25 at 1 GHz
It was dB.

(Example 2) A PVC compound as an unshielded resin was prepared in the same manner as in Example 1. For 100 parts by weight of this PVC compound, coercive force of 50 Oe
, Saturation magnetic flux density 100emu / g, maximum permeability 100 (-) when using powder dispersion coating film, average long axis diameter 20μm, thickness 2-3μm 78 Permalloy (78.5% Ni
300 parts by weight of —Fe) powder was kneaded with a heating two-roll to prepare a compound containing 78 permalloy powder as a magnetic shield resin. The magnetic shield performance of this compound was able to reduce the magnetic field strength of 50 to 100 G (Gauss) to about 1/5 when the thickness was 2 mm. next,
With a mold clamping force of 50 tons and a maximum injection capacity of 160 gf, the primary injection unit injects the mold parting surface from the vertical direction, the secondary injection unit injects the mold parting surface from the horizontal direction, the tertiary injection The injection unit is a sprue bush injection from the fixed plate of the mold, the two-color injection molding machine with the mold rotating device arranged on the side of the movable plate of the molding machine: All Rounder 270M 500-2
Using 10x2 (see above), using a mold placed 120 ° symmetrically around the rotation axis in one side of the mold, the first shield resin layer (thickness 1 mm), non-shield resin Layer (Thickness 1m
m) and the second shield resin layer (thickness 1 mm) were injection-molded in this order to integrate the three layers. The molding cycle was performed 4 times / minute. The finished product had a thickness of 6 mm and a diameter of 100 mm, and the interface between the first shield resin layer and the non-shield resin layer and the non-shield resin layer and the second shield resin layer were completely adhered, and the destruction was forcibly attempted. However, any position other than the interface was broken. When the magnetic shield characteristics were measured, the magnetic field strength of 50 to 100 G (Gauss) was reduced to about 1/10, and the thickness of the shield resin layer was constant compared to the case of the magnetic shield resin layer alone. Despite this, a twofold improvement in magnetic shielding performance was measured.

[0016]

EFFECTS OF THE INVENTION According to the present invention, 1) an electromagnetic wave or magnetic shield resin molded body having a multilayer structure of a shield resin layer and a non-shielded resin layer can be molded by a single mold, so that a plurality of conventional molds can be used. The cost of the mold can be reduced compared to what was needed. 2) Since the third injection and the second injection can be performed at the same time as the second injection, the molding cycle can be doubled or tripled compared to the conventional one-color-by-color molding. No moving work or insert work is required, and the manufacturing cost can be greatly reduced. 3) Unlike the conventional method, after molding one color at a time, there is no need for secondary processing such as fitting and bonding, so the product cost can be greatly reduced.

[Brief description of drawings]

1 (a) and 1 (b) are vertical cross-sectional views showing different aspects of a resin molding obtained by the method of the present invention.

FIG. 2 is a vertical cross-sectional view illustrating the method of the present invention.

FIG. 3 is a vertical sectional view showing an example of a resin molded body obtained by a conventional method.

FIG. 4 is a vertical sectional view showing another example of a resin molded body obtained by a conventional method.

5 (a) and 5 (b) are vertical cross-sectional views showing still another mode of a resin molded body obtained by a conventional method.

[Explanation of symbols]

1 ... Resin molding for electromagnetic wave shield, 2, 2a, 2b ...
Shield resin layer, 3a, 3b ... Non-shield resin layer,
4 ... Magnetic shield resin molding, 21 ... Shield resin layer cavity, 22 ... Non-shield resin layer cavity, 23 ...
Rotating shaft, 24 ... primary injection unit, 25 ... shield resin layer, 26 ... movable plate side mold, 27 ... fixed plate side mold, 28 ... mold parting surface 29 ... secondary injection unit 31 ... conductive Resin molding, 32 ... resin layer not containing conductive filler, 41 ... shield case,
42: inner cylinder, 43: outer cylinder,
44 ‥ insulating resin layer, a resin molded body for 51 ‥ electromagnetic shielding, 52, 52a, 52 b ‥ shield resin layer, 53 ‥ unshielded resin layer, 54 ‥ magnetic shielding molded _{resin, t 1, t 2, t} 3 , T ₄ , t ₅ , t ₆ , t ₇ ... Plate thickness, r ₁ , r ₂ ... Outer diameter.

Claims (1)

[Claims] 1. An electromagnetic wave characterized in that a resin layer having a shielding function and a resin layer having no shielding function are integrated as a multi-layered structure of both resin layers by a two-color or three-color injection molding machine. Manufacturing method of resin molded body for magnetic shield.