JPS60257234A - Electromagnetic wave shielding film and manufacture thereof - 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 [Field of Industrial Application] The present invention relates to an improved electromagnetic shielding film and a method for manufacturing the same.

[Prior art]

In recent years, ICs, especially L8, have come to be used not only in electronic devices but also in various household devices.
Problems such as the destruction of In order to eliminate these problems, it is effective to use conductive plastic as the packaging film or molded body of the trap.

As conductive molded bodies of such conductive films, various types of thermoplastic resins have been used which are completely mixed with a conductive photonic agent or whose surfaces are coated with a conductive material.

Metal fine particles, metal fibers, metallized glass fibers, carbon fibers, carbon fine particles, etc. have been used as conductive photonic agents. However, electromagnetic wave shielding films containing conductive optical fillers require a large amount of filler to obtain high conductivity, have extremely poor film properties, and are difficult to form into thin films of 10 μm or less.

Furthermore, although these conductive plastics are effective in shielding radio waves by reflecting electric fields, their magnetic shielding effects are not particularly high.

In order to improve the magnetic shielding effect, it is effective to use a molded body made of plastic containing ferrite or a composite of composite ferrite fibers.

However, in this case as well, it is necessary to increase the electrical conductivity of the molded product, and the current situation is that it is used in combination with a suitable conductor such as a wire mesh, and the ferrite content is left high in order to particularly enhance the shielding effect. When formed into a film, the film loses its strength and cannot be used. For this reason, there is a demand for an electromagnetic shielding material that is in the form of a film, has a high ferrite content, and has a high film conductivity.

On the other hand, the present inventors have developed a new conductive film and its manufacturing method using polypyrroles and polythiophenes, which produce highly conductive films through electrolytic polymerization among conductive polymer substances (Japanese Patent Application No. 186991/1983). No. 5B
-213201, 5B-213204).

In other words, a conductive polymer film produced by electrolytic polymerization is usually made by placing an electrode substrate in a solution containing an aromatic compound that becomes a monomer for electrolytic polymerization and an electrolyte for conducting electricity in an organic solvent such as acetonitrile. It is formed by a button that can be inserted together with a button to apply electricity between both electrodes. At this time, if the electrode substrate is coated with an insulating polymer film, it will naturally not be possible to conduct electricity and no conductive film will be formed.

However, the present inventors have already shown that by coating various polymer films on electrode substrates and combining them with an appropriate electrolytic reaction solution that does not dissolve the films, the electrolytic reaction proceeds in the same way as on ordinary electrodes. I found it.

Although various plastic films can be made highly conductive by this method, the resulting films only have an electromagnetic shielding effect comparable to that of ordinary carbon-containing plastic materials, and are particularly inferior in magnetic shielding effect.

[Purpose of the invention]

The present invention was made to solve these drawbacks, and its purpose is to provide a film with high electromagnetic shielding properties and a method for manufacturing the same.

[Structure of the Invention] To summarize the present invention, the first invention of the present invention relates to an electromagnetic shielding film, which comprises a ferrite powder or a composite ferrite fiber and an aromatic compound obtained by electrolytic polymerization of an aromatic compound. It is characterized by being made of a polymer film containing a molecular material.

Further, the second invention of the present invention relates to a method for manufacturing an electromagnetic shielding film, which includes a step of coating a polymer film containing ferrite powder or polymerized ferrite fiber on an electrode, and an aromatic film on the electrode with the film. It is characterized in that it includes each step of electrolytically polymerizing a system compound.

When electrolytically polymerizing an aromatic compound on an electrode coated with a polymer film, the aromatic conductive polymer material is uniformly formed on the entire surface of the polymer film, and the aromatic In order to control the growth of polymeric materials, it is necessary to precisely control electrolytic polymerization conditions. Therefore, it is not easy to make a film in which a different material such as a ferrite material is composited into a polymer film conductive. The present inventors analyzed the correlation between the type and composition of electrolytic polymerization solution, parameters such as electrolysis voltage, and electrode material, and the growth process of aromatic polymer material in the film. The present invention has been achieved by successfully increasing the electrical conductivity of various polymer films mixed with each other by electrolytic polymerization of aromatic compounds.

The ferrite material used may be ferrite powder, or composite ferrite fiber obtained by cutting a film made of ferrite and a polymer material into fibers.

In addition, various thermoplastic resins are useful as a base film to which the ferrite material is composited, since they are moldable.

Such polymer films include polyvinyl chloride resins, namely polyvinyl chloride and various vinyl esters of vinyl chloride, vinyl ethyls, acrylic acid and its esters, methacrylic acid and its esters, maleic acid and its esters, etc. Copolymers with monomers such as esters, fumaric acid and its esters, maleic anhydride, aromatic vinyl compounds including styrene, halogenated vinylidene compounds, acrylonitrile, methacrylonitrile, and propylene can be used. In addition, vinylidene chloride and various vinyl esters, vinyl ethers, acrylonitrile,
Copolymers with methacrylonitrile, vinyl chloride, etc., and copolymers of polyethylene and ethylene with the various monomers mentioned above can also be used. .

Furthermore, polystyrene, copolymers of styrene and the various monomers mentioned above, polyethylene terephthalate, rubber, etc. can also be used.

Furthermore, thermosetting resins such as epoxy resins, melamine resins, urea resins, and acetal resins can also be used to obtain hard shielding materials in the form of seeds.

In addition, aromatic compounds that can be electrolytically oxidized and polymerized include virol, 3-methylvirol, N-methylvirol, thiophene, furan, phenol, thiophenol, selenophene, tellurophene, biphenyl, azulene, p-
ter7enyl, o-teryenyl, p-quarter7enyl, '2-hydroxybiphenyl, diphenyl sulfide, 2-(α-chenyl)thiophene, 2-(α-chenyl)7ran, 2- (2-pyrrolyl)virol, 2-(
2-pyrrolyl)thiophene, 2-phenylthiophene,
α-chenylphenyl ether, β-furyl-α-chenylselenide, 2-(2-pyrrolyl)seleno7ene, 2
Aromatic compounds such as -(2-selenienyl)tellofene, N-vinylcarbazole, N-ethynylcarbazole, methylazulene, and pyrene can be used. Various substituted butadiene compounds, which are not aromatic compounds, can also be used.

On the other hand, various compounds such as organic quaternary ammonium salts, inorganic salts, protonic acids, and esters can be used as electrolytes during electrolytic polymerization. Although acetonitrile-based solvents are usually used, electrolytic polymerization of aromatic compounds is possible.
Any material can be selected as long as it dissolves an appropriate electrolyte.

Furthermore, as a substrate for electrolytic oxidative polymerization, noble metals such as gold, platinum, and palladium, or conductive metal oxides such as tin oxide and indium oxide, or these materials may be plated, vapor-deposited, or spackled onto a suitable substrate. Those deposited by this method can be used, and if they are shaped into a drum, they can be manufactured continuously.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.
The invention is not limited to these examples.

Example 1 Polyvinyl chloride resin and ferrite powder (particle size (L2 ~
A tetrahydrofuran solution was prepared by mixing 5μm'') 1 with a volume ratio of 2:1.100^ of chromium was placed on a glass plate.
On top of that, 1000mm of gold was deposited, and then 2000^ of indium tin oxide was deposited by sputtering to serve as an electrode for electrolytic polymerization. A ferrite-containing polyvinyl chloride film was formed on this electrode to a thickness of 70 μm from the above tetrahydrofuran solution using a doctor blade method.
It was dried in an oven at °C for 20 minutes.

On the other hand, virol (1 mol/l') as an electrolytic polymerization solution,
Tetraethylammonium balatoluenesulfone)
(0.4 mol/l) e-containing tr7 solution in setonitrile-tetrahydrofuran (2:1') was prepared. In this electrolytic polymerization solution, a voltage of 5.5'V, 15
Electricity was applied for a minute to perform electrolytic polymerization of virol. The obtained film had ferrite and polypyrrole dispersed in polyvinyl chloride, and could be easily isolated from the electrode.

When the electrical conductivity of the film was measured, it was found that the film before electropolymerization had a conductivity of 5 × 10-” s/cm (D
Compared to K, the film after electrolytic polymerization had a conductivity of 15 s/cm, which was a 300-fold increase in electrical conductivity. Furthermore 51JBg ~ 5
The high-frequency radio wave attenuation of 00 Mug was approximately -5+IB before electropolymerization, but the film after electropolymerization showed a value of about -15dB, indicating a significant improvement in the electromagnetic wave shielding effect. Nine. Furthermore, the ferrite-containing polyvinyl chloride film before electrolytic polymerization was brittle and easily torn, but the polypyrrole-composite film had the advantage of increased strength.

Example 2 Polystyrene resin and ferrite powder (particle size [12~'
; pwl')t - prepare a mixed sita methyl ethyl ketone solution in a volume ratio of 3:1, apply the solution on the same electrode as in Example 1 by doctor blade method to form a ferrite-containing polystyrene film with a thickness of 80 μm, It was dried in an oven at 100°C for 15 minutes.

On the other hand, thiophene (1.2 mol/
l), Tetrabutylammonium Radruene Sulfo$-) (α4 mol/l) t-ttr7 Setonitrile-Methyl Ethyl Ketone (2:1) solution was prepared. The film-attached electrode was immersed in this electrolytic polymerization solution for 15 minutes, and then current was applied between it and a platinum-plated titanium mesh used as a counter electrode for 20 minutes to perform electrolytic polymerization of thiophene. The resulting film consisted of ferrite and polythiophene dispersed in polystyrene, and could be easily isolated from the electrode. When the electrical conductivity of the film was measured, it increased from 2×10 −8/α before electropolymerization to 1.2 s/α.

Radio wave attenuation of this film f 5 MHz ~ 500 MHz
When measured in the frequency range of z, -5c before electropolymerization
The stain magnetic wave shielding property was improved to -15dB from LB. Also, the film, which was brittle before polymerization, showed better mechanical properties than K containing polythiophene.

Example 3 An uncured epoxy resin (volume ratio 1:1) containing ferrite e having a particle size α of 2 to 5 μm was coated with a cord to a thickness of 25 μm on a Mylar film having a thickness of 20 μm.

After this ferrite-containing epoxy resin layer was cured, it was cut into slits having a width of about 40 μm and then ribbed to form a composite 7-elite fiber fabric.

This composite 7-elite fiber cloth was placed on the same electrode as in Example 1, and a tetrahydrofuran solution containing polyvinyl chloride (100 parts by weight) and n-octyl phthalate (15 parts by weight) was dropped onto the fiber cloth. After leaving it for 4 hours, 1
It was dried in the open at 10° C. for 20 minutes to obtain a polyvinyl chloride resin film containing a composite ferrite fiber cloth with a thickness of 120 μm on the electrode.

On the other hand, virol (1.2 mol/l) was used as the electrolytic polymerization solution.
, tetraethylammonium perchlorate) (0,4
A t-fir acetonitrile-tetrahydrofuran solution was prepared. In this electrolytic polymerization solution, electricity was applied between the film-attached electrode and a platinum-plated titanium mesh used as a counter electrode for 30 minutes to perform electrolytic polymerization of virol.

Isolate the film from the substrate and reduce the electromagnetic wave attenuation to 5 MHz.
When measured in the range of ~500 MHg, -20tlB
The value of was changed. This value is -12 dB before electrolytic polymerization.
This is a significant improvement compared to .

〔Effect of the invention〕

As explained above, according to the present invention, a polymer film containing 7-elite powder or composite ferrite fiber is coated on an electrode, and an aromatic compound is electropolymerized on the electrode with the film, thereby producing ferrite. Since a highly conductive polymer film containing a conductive aromatic polymer material and a conductive aromatic polymer material can be obtained, it has the advantage of exhibiting high electromagnetic shielding properties.

Further, there is an advantage that the strength of the composite film in a thin film state can also be improved.

Patent applicant: Nippon Telegraph and Telephone Corporation Agent Hiroshi Nakamoto Same as Akira Inoue Douyoshi Mine Katsura -

Claims (1)

[Scope of Claims] 1. An electromagnetic shielding film comprising a polymer film containing ferrite powder or composite ferrite fiber and an aromatic polymer material obtained by electrolytic polymerization of an aromatic compound. It is characterized by including the steps of coating a polymer film containing ferrite powder or composite ferrite fiber on the Z electrode, and performing electrolytic polymerization for aromaticization on the electrode with the film. Method for manufacturing electromagnetic shielding film.