| 摘要 |
PURPOSE:To prevent a peak from generating in a high frequency and to improve in inherent sound by using a metallic material in which phosphorus compound is produced at least in some part of a fine pore of an anodic oxide film. CONSTITUTION:An Al foil 1 is anodized to produce an anodic oxide film 2 thereon. Having formed said film 2 in this way, the foil 1 is processed by a secondary electrolytic treatment with use of an aq.sol. of ammonium phosphate to produce a phosphorus oxide. Thus some part of the film 2 turns out to be a part 3 where the phosphorus oxide enters in the fine pore (oxide film layer contg. phosphorus oxide). Besides the above method, it is also applicable that with use of an appropriate means an phosphorus compound is filled in the fine pore, or said pore is sealed with the phosphorus compound. Once this diaphragm is made available, it phosphorus compound produced in the anodic oxide film may promote both a high elasticity and low resonance of a metallic material, and therefore the occurrence of a peak in a high frequency can be prevented, which is caused by enhancing the resonance sharpness of the metallic material, and an inherent sound can be improved. |
