| 摘要 |
PURPOSE:To increase the time constant of attenuation of a potential difference impressed on a gap, by a method wherein a groove cut to a predetermined depth from a head surface is provided in a predetermined width in the periphery of a multi-needle electrode, inclusive, and an insulating layer is provided on the entire region of the head surface exclusive of the groove. CONSTITUTION:The multi-needle electrode 3 and a controlling electrode are surrounded by a molded resin body 6 constituting a supporting member, the entire region of the electrode surfaces is finished by polishing, and a coating material based on fluorine is applied onto the entire region of the head surface in a thickness of 2mum as an insulating layer, and is hardened at normal temperature. Then, the groove is formed beneath the electrode 3 to constitute a gap part 12. Since the gap part is constituted of the groove 12 and an arbitrary height is obtained, it is unnecessitated to provide a spacer with a large thickness, and the insulating layer 11 can be provided with an arbitrary thickness. Accordingly, the composite capacitance of the insulating layer 11 and a dielectric layer beneath the controlling electrode 4 can be set high. |
