Near-field noise suppression film

Abstract

A noise suppression film having reduced unevenness of electromagnetic wave noise absorbability, which comprises a thin Ni film, which is vapor-deposited on one surface of a stretched plastic film of polyethylene terephthalate, and then subject to a heat-shrinkage-causable heat treatment at a temperature in a range of 110-170° C. for 10 minutes to 1 hour, (a) the light transmittance of the thin Ni film measured with laser rays having a wavelength of 660 nm being 3-50%, and (b) the surface resistance of the thin Ni film being 10-200 Ω / square when measured on its square test piece TP of 10 cm×10 cm under a load of 3.85 kg applied via a flat pressure plate, with a pair of electrodes each having a length completely covering a side of the test piece disposed on opposing side portions of the test piece.

Description

FIELD OF THE INVENTION[0001]The present invention relates to an inexpensive noise suppression film capable of absorbing near-field electromagnetic waves of several hundred MHz to several GHz in mobile information terminals such as mobile phones and smartphones, electronic appliances such as personal computers, etc.BACKGROUND OF THE INVENTION[0002]Recently, mobile communications terminals, electronic appliances, etc. having various functions and high performance have been getting required to be smaller and lighter, so that their electronic parts are arranged in a narrower space at higher density, with their speeds increasing. Accordingly, among circuits and parts, electromagnetic wave noises, particularly high-frequency noises of several hundred MHz to several GHz have become serious problems. To suppress such near-field electromagnetic wave noises, various noise suppression films have been proposed and put into practical use.[0003]Many of such noise suppression films contain magneti...

AI Technical Summary

Benefits of technology

The present invention provides an inexpensive noise suppression film that can effectively absorb electromagnetic waves (up to several millionHz) for use in mobile communications terminals and electronic appliances. The film is made by depositing a thin layer of Ni film onto a plastic film using vapor deposition and heat treatment. The heat treatment improves the electromagnetic wave absorbability of the Ni film, while reducing its unevenness and change over time. This film can provide stable noise suppression without being affected by heat or abrasion.

Problems solved by technology

(1) When a thin Ni film formed on a plastic film by a vapor deposition method has surface resistance of several tens of n / square, it has excellent absorbability of near-field electromagnetic wave noises, but it is extremely difficult to form such thin Ni films precisely, and actually formed thin Ni films have largely varying surface resistances.

(2) The surface resistance of such thin Ni films is subject to large change with time, so that it takes long until stabilized completely, and that the change with time of surface resistance differs depending on ambient conditions (temperature, humidity, etc.) during that period.

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