JPH0740385A - Manufacture of electromagnetic shielding molded product - Google Patents

Abstract

PURPOSE:To manufacture an electromagnetic wave shielding molded product which is superior in electromagnetic wave shielding properties up to an end wall even if a molding device to manufacture a skin layer is not provided separately. CONSTITUTION:A cavity 3 controlling the outside of an electromagnetic wave shielding hollow molded product 11 by clamping one mold l1 and the other mold 2 and a resin relief part 4 communicating with the cavity 3 through a communicating path 5 are formed and outer layer resin 8 is injected into the cavity 3 through an injection nozzle 6. Then the electromagnetic wave shielding hollow molded product 11 into which an inner layer 9a is interposed is manufactured so as to cross an end wall 11b by extruding in order the outer layer resin 8 and inner layer resin 9 to the resin relief part 4, by a method wherein a pressurizing fluid is pressed into the inner layer resin 9 while injecting or after injection of the inner layer resin 9 within the outer layer resin 8, a small hollow part 10 is formed and in succession the small hollow part 10 is expanded away by pressing the pressurizing fluid into the small hollow part 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an electromagnetic wave shielding molded product which is required to have good electromagnetic wave shielding properties such as a personal computer, a word processor, an electronic measuring instrument, a housing of an electronic musical instrument.

[0002]

2. Description of the Related Art Conventionally, methods (a) and (b) described below have been proposed as a method for manufacturing a laminated molded article having an outer layer and an inner layer made of different materials.

(A) As shown in FIG. 5 (a), a conductive material 104 having a mesh that has been woven or woven beforehand is arranged in one mold 101 and clamped, and then the other is placed in the cavity 103. Method for producing an electromagnetic wave shield molded article in which the molten resin 105 is injected through the resin injection hole 107 of the mold 102 and cooled (see Japanese Patent Laid-Open No. 62-276895).

(B) As shown in FIG. 6 (a), after the injection of the outer layer resin 206 is started through the sprue 205 into the cavity 203 of the molds 201, 202 that have been clamped, as shown in FIG. 6 (b). As shown, the injection of the inner layer resin 207 is started, a predetermined amount is injected into the cavity 203 in a state where the periphery of the inner layer resin 207 is covered with the outer layer resin 206, and then gas injection is performed as shown in (c) of FIG. By blowing a compressed gas into the inside resin 207 through the hole 208, a hollow resin molding in which the periphery of the inside resin layer 207a is covered with the outside resin layer 206a along the cavity 203 as shown in FIG. 6 (d). Method for manufacturing the product 210 (Japanese Patent Application Laid-Open No. 3-28)
4915 publication).

[0005]

However, among the above-mentioned conventional techniques, (a) requires a separate molding device for knitting or weaving a conductive material having a mesh, and therefore the equipment cost is low. Get higher

Further, in (b), since the compressed gas is blown into the inner layer resin and the inner layer resin is covered with the outer layer resin to flow only in the cavity to form a hollow portion, a hollow molded article is obtained. Since the outside of the peripheral end wall is entirely covered with the outer resin layer, it is difficult to interpose the inner resin layer across the outer resin layer outside the end wall.
It is difficult to manufacture an electromagnetic wave shielding molded product which is required to have an excellent electromagnetic wave shielding property also in the end wall portion.

The present invention has been made in view of the above-mentioned problems of the prior art, and the electromagnetic wave shielding property up to the end wall is achieved without separately providing a molding device for manufacturing the skin layer. It is an object of the present invention to realize a method for producing an excellent electromagnetic wave shielding molded product.

[0008]

In order to achieve the above object, the method for producing an electromagnetic wave shielding molded article according to the present invention comprises an inner layer made of a resin having an excellent electromagnetic wave shielding property and a resin having an excellent surface appearance. A method of manufacturing an electromagnetic wave shielding molded article in which an outer layer is laminated, wherein a cavity for controlling an outer surface of the electromagnetic wave shielding molded article and a portion of the cavity for regulating an end wall of the electromagnetic wave shielding molded article. Using a split-type mold having a resin escape portion communicated with the mold, after the mold is clamped, a molten resin forming an outer layer made of the resin excellent in surface appearance is injected into the cavity. Then, while injecting or after injecting a molten resin forming an inner layer made of the resin excellent in electromagnetic wave shielding property into the inside thereof, a pressurized fluid is pressed into the inside thereof to form a hollow portion, thereby forming the hollow portion. The molten resin and the molten resin constituting the inner layer constituting the outer layer of sequential excess and simultaneously molded along the Activity is characterized in that the push to the resin relief portion.

The molten resin forming the inner layer is pushed out to the resin escape portion by injection of the molten resin forming the inner layer without using a pressurized fluid.

[0010]

By pressurizing the fluid under pressure into the molten resin that is injected into the molten resin that forms the outer layer that is made of the resin having excellent surface appearance and that is formed as the inner layer that is made of the resin that has excellent electromagnetic wave shielding properties. A hollow portion is formed, but as the hollow portion expands, excess molten resin forming the outer layer is extruded into the resin escape portion, and when the hollow portion expands to a shape along the cavity, the melt forming the inner layer is melted. The resin is also pushed out to the resin escape portion. As a result, it is possible to manufacture an electromagnetic wave shielding molded product in which the inner layer is interposed so as to traverse the outer layer near the boundary between the end wall of the electromagnetic wave shielding molded product and the wall.

When the pressurized fluid is not used, the inside of the cavity is pressurized by the injection of the molten resin forming the inner layer, but the same molding is achieved by pushing it out into the resin escape portion as the amount of resin increases. To be done.

[0012]

Embodiments of the present invention will be described with reference to the drawings.

(First Embodiment) First, a mold used in this embodiment will be described.

As shown in FIG. 1, the mold is a split mold composed of one mold 1 and the other mold 2, and one mold 1 is an electromagnetic wave shielding hollow product which is an electromagnetic wave shielding molded product. A concave portion 1a that regulates the outer surfaces of the one wall 11a and the end wall 11b of the molded product 11 and an annular concave portion 1b that surrounds the concave portion 1a are provided, and the other mold 2 has a surface appearance to be described later that is injected from an injection nozzle 6. A molten resin (hereinafter referred to as “outer layer resin”) 8 that constitutes an outer layer made of an excellent resin and a molten resin that constitutes an inner layer made of a resin excellent in electromagnetic wave shielding properties (hereinafter,
It is called "inner layer resin". ) 9 and a cavity surface 2a that regulates the outer surface of the other wall 11c of the electromagnetic wave shielding hollow molded product 11 are provided. As a result, the communication path 5 communicates with the cavity 3 that controls the outer surface of the electromagnetic wave shielding hollow molded product 11 when the mold is clamped, and the part of the cavity 3 that controls the end wall 11b of the electromagnetic wave shielding hollow molded product 11. The resin escape portion 4 is formed.

Next, the process of this embodiment will be described.

As shown in FIG. 1A, one mold 1 and the other mold 2 are clamped, and the outer layer resin 8 is injected into the cavity 3 from the injection nozzle 6 by a predetermined amount.

Then, as shown in FIG.
While injecting the inner layer resin 9 from the injection nozzle 6 into the outer layer resin 8 or after injecting it, a pressurized fluid such as pressurized air or nitrogen gas is pressed into the inner layer resin 9 to form a small hollow portion. 10 forms the small hollow portion 1
By forming 0, a small amount of the outer layer resin 8 is pushed out to the resin escape portion 4 through the communication passage 5.

After that, the small hollow part 10 is expanded by injecting the pressurized resin while injecting the inner layer resin 9 or after injecting the inner layer resin 9 to extend along the cavity 3 as shown in FIG. 1C. Hollow part 1
The electromagnetic wave shielding hollow molded product 11 having 0a is molded, but as the small hollow portion 10 expands, the surplus outer layer resin 8 is pushed out to the resin escape portion 4 through the communication passage 5 to form a shape along the cavity 3. When the hollow portion 10a expands, the inner layer resin 9 is also pushed out to the resin escape portion 4 through the communication passage 5. Therefore, the electromagnetic wave shielding hollow molded product 11 having the inner layer 9a interposed near the boundary between the end wall 11b and the other wall 11c of the electromagnetic wave shielding hollow molded product 11 is molded.

(Second Embodiment) First, a mold used in this embodiment will be described.

As shown in FIG. 2, the split mold is composed of one mold 21 and the other mold 22, and one mold 21 is an electromagnetic wave shielding hollow molded product 31 which is an electromagnetic wave shielding molded product. The cavity 21 of the other mold 22 is slidably fitted into the stepped recess 21a for forming the one wall 31a and the resin escape portion 24 and the insertion hole 25a provided in the vicinity of the step of the recess 21a. A slide member 25 that can move back and forth toward the surface 22a is provided, and the outer mold resin 2 that is injected from an injection nozzle 26 to the other mold 22.
8 and an inlet 27 for introducing the inner layer resin 29 and a cavity surface 22a for restricting the outer surface of the other wall 31c of the electromagnetic wave shielding hollow molded article 31 are provided. Thereby, when the mold member is clamped and the slide member 25 is advanced so as to come into contact with the cavity surface 22a of the other mold 22, the cavity for restricting the outer surface of the electromagnetic wave shielding hollow molded product 31 and the resin escape portion 24 are described above. The stepped recess 21a is defined.

Next, the steps of this embodiment will be described.

As shown in FIG. 2A, one mold 21 and the other mold 22 are clamped, and the slide member 25 is advanced by a driving means (not shown) so that the tip of the slide member 25 is moved to the other mold 22. Cavity surface 22
The stepped concave portion 21a is divided into the cavity and the resin escape portion 24 by bringing the outer layer resin 28 into contact with the a or by approaching the outer layer resin 28 to such an extent that there is a gap in which the outer layer resin 28 does not flow. A predetermined amount is injected into the cavity.

After that, the slide nozzle 25 is retracted so that the resin escape portion 24 and the cavity are communicated with each other.
The small hollow portion 30 is formed by injecting a pressurized fluid into the inner layer resin 29 while or after injecting the inner layer resin 29 from 6, and by forming the small hollow portion 30, a small amount of the outer layer resin 28 is formed. Are extruded into the resin escape portion 24.

Next, the electromagnetic wave shielding hollow molded product 3 having the hollow portion 30 a having a shape along the cavity is expanded by expanding the small hollow portion 30 by continuously pressurizing the pressurized fluid while re-advancing the slide member 25.
1 is molded, but as the small hollow portion 30 expands, the surplus outer layer resin 28 is pushed out to the resin escape portion 24, and when the hollow portion 30a expands to a shape along the cavity, the inner layer resin 29 also. It is pushed out to the resin escape portion 24. Therefore, the end wall 31 of the electromagnetic wave shielding hollow molded product 31
The electromagnetic wave shielding hollow molded product 31 with the inner layer 29a interposed at the boundary between the wall b and the other wall 31c is molded.

After that, as shown in FIG. 2C, the slide member 25 is attached to the cavity surface 22 a of the other mold 22.
The outer surface of the end wall 31b of the electromagnetic wave shielding hollow molded product 31 is shaped by advancing until it comes into contact with. In this case, if the tip of the slide member 25 is set to a sharp angle,
The tab made of excess resin extruded from the end wall 31b to the resin escape portion 24 can be cut off in the mold.

(Third Embodiment) First, a mold used in this embodiment will be described.

As shown in FIG. 3, the mold is a split mold consisting of one mold 51 and the other mold 52, and one mold 51 has one wall 61 of an electromagnetic wave shielding molded product 61.
a and a ring-shaped recess 51b that surrounds the recess 51a for restricting the outer surfaces of the end wall 61b and the other mold 52.
Of an injection port 56 for introducing an outer layer resin 58 made of a resin having a good surface appearance described later and an inner layer resin 59 made of a resin having an excellent electromagnetic wave shielding property, which is injected from an injection nozzle 56, and an electromagnetic wave shielding molded product 61. A cavity surface 52a that regulates the outer surface of the other wall 61c is provided. As a result, the resin that is communicated by the communication passage 55 to the cavity 53 that regulates the outer surface of the electromagnetic wave shielding molded product 61 when the mold is clamped and the portion that regulates the end wall 61b of the electromagnetic wave shielding molded product 61 within the cavity 53. The escape portion 54 is formed.

Next, the process of this embodiment will be described.

As shown in FIG. 3A, one mold 51 and the other mold 52 are clamped, and the outer layer resin 58 is injected into the cavity 53 from the injection nozzle 56.
A predetermined amount is injected into 3.

Then, as shown in FIG. 3B,
Although the amount of resin in the cavity is increased by injecting the inner layer resin 59 from the injection nozzle 56 into the outer layer resin 58, a small amount of the outer layer resin 58 passes through the communication passage 55 due to the pressurization in the cavity due to the increase in the amount of resin. It is pushed out to the resin escape portion 54.

After that, by subsequently injecting the inner layer resin 59, an electromagnetic wave shielding molded product 61 having a shape along the cavity 53 is molded as shown in FIG. 3C, but the inside of the cavity is pressurized. As it goes along, the excess outer layer resin 58 is pushed out to the resin escape portion 54 through the communication passage 55, and when the resin fills the shape along the cavity 53, the inner layer resin 59 also passes through the communication passage 55 and the resin escape portion 5.
Extruded to 4. Therefore, the electromagnetic wave shielding molded product 61
The inner layer 59 is formed near the boundary between the end wall 61b and the other wall 61c.
The electromagnetic wave shielding molded product 61 in which a is interposed is molded.

Here, an example of the electromagnetic wave shielding molded product manufactured by each of the above embodiments will be described.

FIG. 4 is a plan view of the electromagnetic wave shielding hollow molded product of this example, which is a rectangular electromagnetic wave shielding hollow molded product 4 in plan view.
1 is a communicating portion 43 on each of the end walls at both ends in the longitudinal direction.
Has a tab 42 connected by, and a portion surrounded by a two-dot chain line is a portion 41b having an outer layer and an inner layer and has excellent electromagnetic shielding property, and an outer portion of the two-dot chain line, that is, a side portion 44 is It is formed in the portion 41a having only the outer layer. Needless to say, in the case of this example, the resin escape portion uses a mold in which the end walls of both ends of the electromagnetic wave shielding hollow molded product 41 are communicated with the cavity portions that regulate the end walls.

The electromagnetic wave shielding hollow molded product 41 of the present embodiment is used, for example, as a housing member constituting a casing of a computer, when it is used by being assembled to another member, it is overlapped with another member,
It is used when the side portion 44 is arranged as a portion to which a separate electromagnetic wave shielding measure is applied, that is, a portion where the shielding measure is not required.

The electromagnetic wave shielding molded product according to the present invention is not particularly limited in its use, but a preferred example is a housing panel for electronic equipment.

In the present invention, the resins constituting the inner and outer layers are ABS resin, AS resin, polypropylene, modified polyphenylene oxide, polycarbonate, polyamide, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, and other injection-moldable thermoplastic synthetic resins. A resin is used as appropriate.

The resin constituting the inner layer is made of fiber, carbon in the form of flakes or powder,
It is a mixture of conductive fillers such as iron, copper, brass and aluminum.

Above all, the thickness is 5 to 160 μm and the length is 0.1.
It is preferable to mix 5 to 50 parts by weight of conductive fibers such as carbon, iron, copper, brass, and aluminum having a size of 4 mm with respect to 100 parts by weight of the resin.

On the other hand, as the resin constituting the outer layer, a pigment such as gray or blue is mixed, and the melt viscosity at the time of molding is higher than that of the resin constituting the inner layer, and the same kind of resin as the resin constituting the inner layer is used. Is preferable in terms of moldability, deformation resistance and adhesiveness. For example, when the resin forming the inner layer is ABS resin,
The resin that constitutes the outer layer is an ABS resin, an AS resin, a blend of an ABS resin and a polycarbonate, polythretin, or the like.

The resin containing a conductive filler such as carbon fiber achieves the purpose of imparting electromagnetic wave shielding properties, but on the other hand, the conductive filler is exposed on the molding surface,
Moreover, since the mold reproducibility is impaired by the conductive filler, there is a problem that the surface appearance is poor.

In the present invention, the outer surface can maintain the appearance surface of the molded article which is generally damaged by the conductive filler. Since the molded product obtained by the present invention has excellent surface appearance, there is an effect that surface treatment before coating can be simplified even if the molded product is finally coated.

In addition, in the molded article having the hollow portion according to the present invention, the resin as the inner layer is moved by the expansion of the hollow portion during the manufacturing, so that the inner layer flows toward the end surface of the molded article and the electromagnetic wave is generated. In addition to excellent shielding properties, it is possible to achieve reduction of expensive materials and weight reduction of molded products.

[0043]

Since the present invention is configured as described above, it has the following effects.

Since an inner layer made of a resin having an excellent electromagnetic wave shielding property is interposed so as to cross the end wall of the electromagnetic wave shielding molded product, an electromagnetic wave shielding molded product having an excellent electromagnetic wave shielding property up to the end wall can be obtained. It can be manufactured.

Further, since the molding can be carried out in the same cavity, it is not necessary to separately install a molding device for molding the skin layer as in the conventional case.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a mold showing each step of the first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a mold showing each step of the second embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view of a mold showing each step of the third embodiment of the present invention.

FIG. 4 is a schematic plan view showing an example of an electromagnetic wave shielding hollow molded product manufactured according to the present invention.

FIG. 5 is a schematic cross-sectional view of a mold showing steps of an example of a conventional method for producing an electromagnetic wave shield molded product.

FIG. 6 is a schematic cross-sectional view of a mold showing steps of another example of the conventional method for manufacturing a laminated hollow molded article.

[Explanation of symbols]

 1, 1, 51 One mold 1a, 21a, 51a Recess 1b Annular recess 2,22, 52 Other mold 3,53 Cavity 4, 24, 54 Resin escape part 5 Communication passage 6, 26, 56 Injection nozzle 7, 27 , 57 inlet port 8, 28, 58 outer layer resin 8a, 28a, 58a outer layer 9, 29, 59 inner layer resin 9a, 29a, 59a inner layer 10, 30 small hollow portion 10a, 30a hollow portion 11, 31, 41 electromagnetic wave shielding hollow Molded product 11a, 31a, 61a One wall 11b, 31b, 61b End wall 11c, 31c, 61c Other wall 41a Part having only outer layer 41b Part having outer layer and inner layer 42 Tab 43 Communication part 44 Side part 61 Electromagnetic wave shielding property Molding

Claims (2)

[Claims] 1. A method for producing an electromagnetic wave shielding molded article, which comprises an inner layer made of a resin having an excellent electromagnetic wave shielding property and an outer layer made of a resin having an excellent surface appearance layered together, the electromagnetic wave shielding molded product. The mold is clamped using a split-type mold having a cavity for regulating the outer surface of and a resin escape portion communicating with a portion of the cavity for regulating the end wall of the electromagnetic wave shielding molded product. After that, while injecting a molten resin constituting the outer layer made of the resin having excellent surface appearance into the cavity, and then injecting a molten resin constituting the inner layer made of the resin having excellent electromagnetic wave shielding property into the cavity Alternatively, after injection, a pressurized fluid is press-fitted into the inside to form a hollow portion, which is molded along the cavity, and at the same time, the excess molten resin and the inner Method of manufacturing an electromagnetic wave shielding molded product, characterized in that extruding molten resin constituting to the resin relief portion. 2. A method for producing an electromagnetic wave shielding molded article in which an inner layer made of a resin having an excellent electromagnetic wave shielding property and an outer layer made of a resin having an excellent surface appearance are laminated, and the electromagnetic wave shielding molded article is manufactured. The mold is clamped using a split-type mold having a cavity for regulating the outer surface of and a resin escape portion communicating with a portion of the cavity for regulating the end wall of the electromagnetic wave shielding molded product. After that, injecting a molten resin forming an outer layer made of the resin excellent in surface appearance into the cavity, and then injecting a molten resin forming an inner layer made of the resin excellent in electromagnetic wave shielding into the cavity By molding along the cavity, and simultaneously extruding excess molten resin forming the outer layer and excess molten resin forming the inner layer to the resin escape portion. Manufacturing method of shielding molded products.