JPH02125730A - Molding with electromagnetic sealing properties and molded material using same sheet - Google Patents

Abstract

PURPOSE:To make a conductive layer hard to be broken by the stress applied at the time of molding by laminating a conductive laminate sheet, a heat fusion type bonding agent layer of specific thickness and a thermoplastic synthetic resin sheet. CONSTITUTION:A conductive laminate sheet A is provided with conductivity by means of a metal film 1 in a base constitution, and a number of creases are generated in the metal film 1 by the contraction of the heat shrinkable synthetic resin film 2. Accordingly, when a sheet for molding is molded, even if the conductive laminate sheet A is stretched, the creases of the metal film are also stretched to prevent the metal film constituting the conductive layer from getting broken. Also, at the time of molding, although the stretching margin of the conductive laminate sheet A and a thermoplastic synthetic resin sheet C are different, a heat fusion type bonding agent layer B of 30mum-200mum thickness is provided between the two and fluidity is generated in the heat fusion type bonding agent B by the heat of molding and the difference of stretches generated between the conductive laminate sheet A and the thermoplastic synthetic resin sheet C is absorbed by said heat fusion type bonding agent layer B to manufacture a molded product of good appearance.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a molded body having electromagnetic shielding properties used in the housing of electronic equipment, and a molded body suitable for molding this molded body by vacuum forming or pressure forming. The present invention relates to a sheet for molding.

[Conventional technology]

Sheets for molding molded objects that require electromagnetic shielding properties, such as housings for electronic devices, must be electrically conductive. Alternatively, a sheet made by laminating thermoplastic resin and conductive nonwoven fabric is used as a molding sheet.

[Invention tries to solve it! I topic]

However, when the above-mentioned molding sheet is molded by vacuum forming or pressure forming, the molding sheet is greatly elongated, especially at the corners of the mold, so a large stress is applied to the conductor 1tWJ of the molding sheet. , lead T1. N
There is a problem that the molding sheet may break or a crank may occur in the molding sheet. Furthermore, in recent years, such molded bodies are required to have flame resistance.

Therefore, the present invention provides a molding sheet in which a conductive layer that provides electromagnetic shielding properties is difficult to break due to stress applied during molding and has good moldability, and a molding sheet that has good electromagnetic shielding properties when molded with this molding sheet. has
Furthermore, the technical object is to provide a molded article that also has flame resistance.

[Means to solve the problem]

In order to solve the above problems, this invention basically uses a conductive laminate sheet A with a thickness of 30 μm or more as a molding sheet.
A laminate of a 200μ+1 hot-melt adhesive J [B and a thermoplastic synthetic resin sheet C is prepared, and the conductive laminate sheet A is coated with a small amount of gold WAF' (both on one side through an intermittent adhesive layer). It was formed by heat-shrinking a base material laminated with heat-shrinkable synthetic resin films.

The hot-melt adhesive layer B and the thermoplastic synthetic resin sheet C may be provided on one side or both sides of the conductive laminate sheet A.

Furthermore, by imparting flame retardancy to the hot-melt adhesive layer B, the flame resistance of the molding sheet was improved.

(Function) The conductive laminate sheet A has conductivity due to the metal thin film in the base material structure, and many fine wrinkles are generated in the metal film due to shrinkage of the heat-shrinkable synthetic resin film.

Therefore, when the above-mentioned molding sheet is molded, even if the conductive laminate sheet A is stretched, the wrinkles of the metal thin film are stretched, and the gold rfA thin film constituting the conductive layer is prevented from breaking.

In addition, during molding, although the conductive laminate sheet A and thermoplastic synthetic resin sheet C have different elongation margins, since the hot-melt adhesive NB is provided between them, the heating during molding As a result, fluidity is developed in the hot melt adhesive layer B, and the difference in elongation that occurs between the conductive laminate sheet A and the thermoplastic synthetic resin sheet C is absorbed by the hot melt adhesive layer B, and the appearance is improved. A good molded body can be obtained.

In addition, by using a vinyl chloride resin as the thermoplastic synthetic resin sheet C and imparting flame retardancy to the hot-melt adhesive layer B, when the molding sheet is burned, the conductive laminated sheet A and the thermoplastic There is no peeling between the synthetic resin sheets C, and flame retardancy is exhibited as a whole.

In addition, the synthetic resin layer of the gold RF4 thin film is preferably made of heat-resistant polyethylene terephthalate, and during vacuum or pressure molding,
The metal thin film can suppress its own elongation as much as possible, and can provide a high electromagnetic shielding effect without causing cracks in the metal layer.

Furthermore, when the conductive laminate sheet A is composed of a metal thin film in which a synthetic resin layer with a metal vapor deposition layer and metal foil are integrated, or when the conductive laminate sheet A is composed of two or more layers, - A higher electromagnetic shielding effect can be provided.

〔Example〕

The molding sheet according to the present invention is basically composed of a Mi layered body of a conductive laminate sheet A, a hot-melt adhesive WIIB, and a thermoplastic synthetic resin sheet C.

The conductive laminate sheet A is formed by heat-shrinking a base material 5 in which a heat-shrinkable synthetic resin film 4 is laminated on the surface of a metal thin film 1 via an intermittent adhesive layer 3, and is heat-shrinkable. As shown in FIG. 1(a), the synthetic resin film 4 is
It may be provided on both sides of the metal thin film 1, or it may be provided on one side of the metal thin film 1 as shown in FIG. 1(b).

The gold nWi film 1 is simply 3 μm thick as shown in FIG.
The metal foil Ma having a thickness of m to 15III may be used alone.
Moreover, the metal thin film 1 is a synthetic tree 1]IJi 2 0.0
2 μm to 3 μm thick metal vapor deposited layer, or 3p+5-15
In other words, in FIG. 2 ([+), a metal vapor deposited layer Tlb or a metal foil Ma is formed on both sides of the synthetic resin layer 2, respectively. In FIG. 2 (8), a metal vapor deposition layer Mb or a metal foil Ma is formed on one side of the synthetic resin layer 2.

Furthermore, the metal thin film 1 may be formed by forming a metal vapor deposited layer on the synthetic resin layer 2, or by laminating and integrating a metal foil. 1 Mb of metal vapor deposition is formed on one side, and gold n is deposited on the other side.
It is an integrated version of F5 M a, and is shown in Figure 2 (ne).
In this example, metal vapor deposition J1g1Mb is formed on one surface of synthetic resin N2, and metal foil Ma is integrated thereon. Furthermore, Fig. 2 shows the synthetic resin Jl! Metal evaporated N lungs are formed on both sides of i2, and gold IFIS f (
It is an integrated version of iMa.

Note that FIG. 1 (() and (o) show the base material 5 before heat shrinkage, and FIG. 3 shows the state of the base material 5 in FIG. 1 (a) after heat shrinkage. There is.

The metal layer of the metal thin film 1 may be a gold B foil such as aluminum foil or copper foil, or a vapor deposited layer of aluminum or tin.The total thickness of this metal layer is determined to have a sufficient electromagnetic shielding effect after forming. In order to obtain, at least 0.02μ or more is required, preferably 0.1μ or more.
Further, a total thickness of 15 μm or more becomes economically expensive.

The above metal thin ll! 1 synthetic resin N2 is polyethylene,
Single substance or laminate of polypropylene, vinyl chloride, polystyrene, acrylic, polyethylene terephthalate, ethylene-vinyl acetate copolymer, etc., usually 4 to 25
- thickness is used. Preferably, heat-resistant polyethylene terephthalate is used.

In addition, the metal part of the metal thin film 1 and the synthetic resin Jl! In the case of metal foil, the lamination method with 2 may be arbitrary, such as synthetic resin coating or film bonding, and in the case of metal vapor deposition, it may be simply vapor-deposited on the film as the synthetic resin layer 2.

The heat-shrinkable synthetic resin film 4 is polyethylene-based,
It is preferable to use a resin made of polypropylene, vinyl chloride, polystyrene, polyester, etc., which has a shrinkage rate as high as possible, for example, about 50%. others,
It may be a laminate of two or more types of films.

The intermittent adhesive layer 3 may be formed by any means capable of bonding the gold rlA thin film 1 and the shrinkable synthetic resin film 4. In addition to adhesives, the heat-shrinkable synthetic resin film 4
This intermittent adhesion may be performed by intermittent heat fusion or ultrasonic fusion using the characteristics of J! ! The pattern 13 may be linear, dotted, or lattice-like in plan view (the point is that it does not have to be provided on the entire surface but in the intermittent portions 6).
It suffices if the pattern exists.

Next, as the adhesive forming the hot-melt adhesive layer B,
For example, olefin adhesives such as ethylene-vinyl acetate, ethylene-acrylic acid, ester copolymers, ethylene ionomers, polyethylene alone or mixtures can be used.

Furthermore, in order to impart flame retardancy to the molding sheet, the olefin adhesive may contain tricresyl phosphate, trischloroethyl phosphate, tris dichloropropyl phosphate, tris dibromopropyl phosphate, triphenyl phosphate, decabromodiphenyl ether, One or more flame retardants selected from the group of chlorinated paraffin and antimony oxide can be mixed.

The flame retardant has a content of 20 to 70% in the hot-melt adhesive layer B.
% by weight, preferably 40-60% by weight. this is,
This is because if the amount is less than 2011i, no flame retardant effect can be obtained, and if it exceeds 70% by weight, the cost will be high economically.

The thickness of this layer is between 30 μm and 200 Fm, preferably 5
Make it 0 μm to 150 #ll. This is because if it is less than 30μ, the effect of stress buffering due to misalignment during molding cannot be obtained.
Moreover, if it is 20 On or more, the cost becomes economically high.

Further, as the resin forming the thermoplastic synthetic resin sheet C, vinyl chloride type, methyl methacrylate type, acrylonitrile pudadiene styrene type, polystyrene, polycarbonate, modified polyphenylene oxide type, etc. can be used.

Furthermore, in order to obtain flame retardancy, the thermoplastic synthetic resin sheet C is preferably a vinyl chloride-based material with excellent flame resistance.The thickness of this sheet is preferably 3.0 μm to 5.0 μm. is common, but is not limited to this thickness.

Next, the conductive WIN sheet A and the hot melt adhesive JI
As a means of laminating and integrating IIB and thermoplastic synthetic resin sheet C, when extrusion molding thermoplastic synthetic resin sheet C, at the same time as this extrusion, conductive laminated sheet A is coated with a hot melt adhesive layer. There is a method of continuously thermally laminating the conductive laminate sheet A, a hot-melt adhesive layer B, and a thermoplastic synthetic resin sheet C through a layer B, and a method of thermally laminating the conductive laminate sheet A, the hot-melt adhesive layer B, and the thermoplastic synthetic resin sheet C by hot pressing.

When molding the molding sheet configured as described above, the molded body is heated and molded so that the use surface of the molded body becomes the surface of the thermoplastic synthetic resin sheet C of the molding sheet. As a method for this heat forming, a normal vacuum forming method or a pressure forming method can be used.

Next, the effects of each constituent layer when the above molding sheet is molded will be explained based on FIGS. 4 and 5.

First, before molding, the molding sheet is made up of a conductive laminate sheet A and a thermoplastic synthetic resin sheet C that are bonded together via a hot-melt adhesive FIB. After molding, the stretch of the thermoplastic synthetic resin sheet C is greater than the stretch of the conductive laminate sheet A formed by heat shrinkage, especially the corners and rising parts of the mold.
a-a of hot-melt adhesive FJB in Figure 4 before molding
As shown in FIG. 5, the distance between the point and the point bb is stretched after molding, and becomes the point aI-81 and the point b'b', and L becomes La' and Lb'.

At this time, the hot-melt adhesive JiglB develops fluidity due to heating, causing a difference in elongation at both interfaces of the hot-melt adhesive layer B. As a result, the difference in elongation (L<La'<Lb
'), a molded product with a good appearance can be obtained without deteriorating the adhesive performance.

In addition, as long as the metal thin film 1 of the conductive laminate sheet A does not break during molding, even if the heat-shrinkable synthetic resin film 4 breaks, there is no practical problem.

In addition, during molding, when the conductive laminate sheet A is stretched by heat shrinkage within the range of the wrinkles formed by the molding, the wrinkles of the conductive laminate sheet A remain in the molded product at that part.
This is practically impossible.

Next, in the metal thin film 1 of the conductive laminate sheet A, when comparing the metal foil and the synthetic resin layer on which the metal vapor deposited layer is formed, differences are seen in areas beyond the range of wrinkle elongation during molding. . In other words, in the case of a synthetic resin layer on which a metal vapor deposited layer has been formed, elongation occurs continuously, so it does not appear to be broken in appearance, but in the case of metal foil, cracks occur and the metal thin 11fil
rupture may occur. However, from the point of view of electromagnetic shielding properties, excellent effects are obtained even with metal foils with cracks.

From this, in Figure 6 (a), the conductive 8IN seam)
As the metal thin film 1 in A, thermoplastic synthetic resin sheet 1-C
The synthetic resin layer 2 was provided with a gold a foil Ma on the side thereof and a gold B vapor deposited layer Mb on the opposite side.

The molded product obtained in this way has a good surface appearance and a 'r! j.It had a high magnetic shielding effect.

Furthermore, as a method of simultaneously laminating a metal foil and a synthetic resin layer on which a metal vapor deposited layer has been formed, as shown in FIG. A heat-shrinkable synthetic resin film 4 is provided, and intermittent adhesion N3 is applied to both sides of the conductive Wi layer sheet A′ which has been heat-shrinked, and the thin metal M11 having a metal vapor deposition of 1 Mb on at least one side of the synthetic resin layer 2. A conductive laminate sheet A'' which is heat-shrinked with a heat-shrinkable synthetic resin film 4 provided therebetween is shown in FIG.
) may be stacked in this order.

Note that between the conductive laminate sheets A' and A'', heat-shrinkable synthetic resin films 4 may be fused together, or a heat-melting adhesive layer of the same type as B may be provided.

Next, Examples and Comparative Examples of the present invention are shown in Tables 1 and 2, respectively.

In Examples 1 to 3, the appearance of the obtained molded products was good on both the front and back sides. In particular, there was no tearing or peeling of the metal thin film even in some corners of the back side (good results).

In addition, in the case of Example 4, although there were cracks on a part of the back surface, [! H! The shielding effect was very good, and in Example 5.6, a high El'll shielding effect and good appearance on the back surface were obtained.

Next, Example 4.7 uses EVA (MI 0.8 VA cont 20%) as the hot melt adhesive NB.
soma% decabromodiphenyl ether 25〃s
When using a composition with a blend of 0 and 25 #b, flame retardance corresponding to the flame retardant standard UL94-V-0 was achieved.

Further, in Example 5.6, EVA (MIO, 8VA conL 20%) 4 was used as the hot-melt adhesive layer B.
0! ilt% decabromodiphenyl ether 24 1
When a composition of SbxOs 36' was used, flame retardancy corresponding to UL-94-V-0 was achieved.

On the other hand, in the case of Comparative Example 1.3.4.5, the conductive tI layer receipt and the thermoplastic synthetic resin sheet C peeled off at a part of the corner of the back side, which impaired the commercial value in terms of appearance. Ta.

Furthermore, although Comparative Example 2 had good moldability, a sufficient t-magnetic wave shielding effect could not be obtained. Further, during the combustion test, peeling occurred between sheets A and 0, and only flame retardancy corresponding to tIL-944B was exhibited.

In addition, the EMI shielding effect is determined by attaching a molded body to one side of a copper casing and transmitting it from a transmitter installed inside the casing.
An electric field of ~100 Qo was transmitted, and the attenuation value of the electric field strength was measured using a receiving antenna located at a distance of 3 m and a spectrum analyzer.

〔Effect of the invention〕

According to the present invention, as described above, it is possible to obtain a molding sheet in which the conductive layer imparting electromagnetic shielding properties is difficult to break due to stress applied to gaps during molding, and which also has good moldability. This has the effect of providing a molded article with a good appearance without breakage of the electrical layer.

Margin below

[Brief explanation of drawings]

FIG. 1 (G + (II) is a cross-sectional view showing the state before heat shrinkage into a conductive laminated sheet, and FIGS. 2 (a) to (f) are cross-sectional views showing an example of the metal thin film 1, respectively. FIG. 3 is a sectional view showing the conductive laminated sheet A of FIG. 1(A) in a heat-shrinked state, FIG. Fig. 4 is a partial sectional view showing the state of the forming sheet after forming, Fig. 6 (()
, (11) are sectional views showing other embodiments of the molding sheet according to the present invention. A: Conductive laminate sheet, B: Hot-melt adhesive layer, C: Thermoplastic synthetic resin sheet, 1:
・Metal thin film, Ma...Metal foil, Mb...
...Metal deposition layer, 2...Synthetic resin layer,
3...Intermittent adhesive layer, 4...Heat-shrinkable synthetic resin film, 5...
··Base material. Fig. 1 Fig. 5 fJ2 Fig. 4

Claims (9)

[Claims] (1) A conductive laminated sheet A is formed by heating and shrinking a base material in which a heat-shrinkable synthetic resin film is laminated on at least one side of a metal thin film via an intermittent adhesive layer, and at least one of the conductive laminated sheets A is Thickness 30μm to 200μm on one side
A molding sheet having electromagnetic wave shielding properties, which is formed by laminating and integrating thermoplastic synthetic resin sheets C via a hot-melt adhesive layer B. (2) The molding sheet having electromagnetic shielding properties according to claim (1), wherein the metal thin film is a metal vapor-deposited film having a thickness of 0.02 μm to 3 μm formed on at least one side of the synthetic resin layer. (3) The metal thin film is metal foil and has a thickness of 3 μm to 15 μm.
A molding sheet having electromagnetic shielding properties according to claim (1). (4) A claim in which the metal thin film is a synthetic resin layer with a metal vapor deposited film having a thickness of 0.02 μm to 3 μm formed on at least one side and a metal foil having a thickness of 3 μm to 15 μm, which are laminated and integrated. 1) A molding sheet having electromagnetic shielding properties as described above. (5) Claim in which the conductive laminate sheet A consists of two or more layers (
1) A molding sheet having electromagnetic shielding properties as described above. (6) The sheet for molding having electromagnetic shielding properties according to claim 2 or 4, wherein the synthetic resin layer of the metal thin film is a polyethylene terephthalate film. (7) Hot melt adhesive layer B is selected from the group of tricresyl phosphate, trischloroethyl phosphate, tris dichloropropyl phosphate, tris dibromopropyl phosphate, triphenyl phosphate, decabromodiphenyl ether, chlorinated paraffin, and antimony oxide. 2. The molding sheet having electromagnetic shielding properties according to claim 1, which is a polyolefin resin containing 20 to 70% by weight of one or more flame retardants. (8) The molding sheet having electromagnetic wave shielding properties according to claim (1), wherein the thermoplastic synthetic resin sheet C is a vinyl chloride resin. (9) A molded article obtained by molding the sheet for molding according to claim (1).