Recently-developed electronic apparatuses such as computers, personal computers and television sets generate various electromagnetic wave noises of high frequencies, and cause problems of electromagnetic interference (EMI). To solve such problems, techniques for absorbing electromagnetic waves from electronic parts of the electronic apparatuses have been searched.
Various techniques have been disclosed, including Unexamined Published Japanese Patent Application (Tokkai-Sho) No. 50-155999, wherein electromagnetic waves are absorbed by a composite comprising metal magnetic particles and resin Such an electromagnetic wave absorber, however, does not have sufficient absorbency, and thus, sufficient effects cannot be obtained when the absorber is attached to an electronic part that generates electromagnetic waves.
Another disclosure is an electromagnetic wave absorbing sheet comprising a resin layer filled with metal oxide magnetic particles formed on an electroconductive material (Tokkai-Sho 57-129003, Tokkai-Hei 4-234103, and Tokkai-Hei 7-249888). The sheet decays electromagnetic waves by reflecting some of the electromagnetic wave and absorbing other parts thereof. The complicated structure of the sheet, however, raises the production cost. Moreover, the applicable temperature range is narrow because the heat resistance of the resin is low.
Thermoconductive sheets have been disclosed as a part of cooling systems for heat-radiation in exoergic electronic parts of electronic apparatuses (Tokkai-Hei 2-166755, Tokkai-Hei 2-196453, and Tokkai-Hei 6-155517). Many exoergic electronic parts, however, simultaneously have electromagnetic interference caused by electromagnetic wave noise. In such a case, a shielding material other than the thermoconductive sheet, is used to absorb electromagnetic waves. Since plural kinds of parts are necessary, the cost will increase.
USPTO Backgrounds
USPTO Backgrounds