| 摘要 |
PURPOSE:To stably perform oscillation at a prescribed frequency, by providing a resin layer with specific width on the surface of an electrode and having irregularity due to the evaporation of a coating solvent. CONSTITUTION:The resin layer 6 whose width is 1-10% of oscillation wavelength and having the irregularity of 1-10% of the oscillation frequency formed by the evaporation of the coating solvent is provided on the surface of the electrode 2. When the thickness of the insulating epoxy resin layer 6 is larger than the above range, the oscillation of a basic wave is weakened by absorption and scattering at the insulating epoxy resin layer 6. Also, when it is smaller, an incidental vibration wave can be easily oscillated by imperfect phase unmatching degree for incidental vibration. In such a way, it is possible to suppress only the oscillation of the incidental vibration wave without necessitating a specific device easily and inexpensively and without suppressing the oscillation of a required frequency.
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