| 摘要 |
PURPOSE:To produce an electret filter enhanced in surface electric charge density, with the surface electric charge unformly distributed, having high collection efficiency since the surface is not deteriorated by oxidation and excellent in stability of the collection efficiency in high yield. CONSTITUTION:An electric charge is impressed from a charging electrode 3 on nonwoven fabric 1 which is thereby turned into an electret, and an electret filter is produced. In this case, a gas is blown against the nonwoven fabric 1 from the rear of the charging electrode 3, an electric charge is impressed on the nonwoven fabric 1 from the charging electrode 3, and the electret filter is produced. |
