| 摘要 |
PURPOSE:To obtain an electret filter whose high adsorption performance is stabilized for a long period and having excellent durability by allowing the surface of a fibrous sheet to retain >=0.2eV electric charge as the activation energy of the polarization charge. CONSTITUTION:A fibrous sheet is formed by using a raw material having >=10<13>OMEGAcm resistivity, and the inside of the sheet is allowed to retain >=7X10<-11>c/cm<2> electric charge as the polarization charge. The polarization charge constituting the electric charge has at least 0.2eV activation energy. A fibrous sheet 10 is placed on a water electrode 11, and a high voltage DC current is impressed thereon by using an acicular electrode 12 to form the electric charge. When the distance between both electrodes is 3cm, 10kV and >=0.1sec time of impression are preferable. The diameter of the fiber of the sheet is regulated to <=20mu, the amt. of the fiber is controlled to 80g/m<2>, and the apparent density is preferably adjusted to 0.05g/cm<3>. |
