| 摘要 |
PURPOSE:To prevent dust collecting rate from lowering with time by laminating insulated layers and conductive layers one after another and forming a space layer between one conductive layer and a layer facing to said conductive layer larger than a space layer between the other conductive layer and a layer facing to the other conductive layer. CONSTITUTION:At least a first insulated layer 3, a first conductive layer 1, a second insulated layer 4 and a second conductive layer 2 are laminated one after another. A space layer t3 between the conductive layer 2 and the insulated layer 4 is made larger than other space layers t1 and t2. Thus, most of air is passed through the large space layer and charged dust is adhered only on the surface of the charged layer, not adhered on the surface of the insulated layer, so that an electric field of the space layer between the conductive layer and the insulated layer is not relaxed and dust collecting rate is not lowered with time. |
