| 摘要 |
PROBLEM TO BE SOLVED: To increase the capacitance of an electrolytic capacitor by eliminating uneven electrolytic etching of Al foil by specifying the wave number of an oxide coating film formed on the surface of the foil with a specific thickness measured with an infrared spectrophotometer before electrolytic etching. SOLUTION: Aluminum foil carries an oxide coating film of 30-60Åin thickness on its surface before electrolytic etching. The thickness of the oxide coating film on the surface of the foil can be measured relatively easily with accuracy when the X-ray photoelectron spectroscopy is used. The quality of the oxide coating film, on the other hand, can be measured from the position, namely, the wave number of the peak of reflection of infrared absorption spectra when the oxide coating film is analyzed by using parallel polarized light made incident at an incident angle of 75 deg. with a Fourier transform infrared spectrophotometer by using parallel polarized light made incident at an incident angle of 75 deg.. When the wave number of the peak of reflection of the oxide coating film on the surface of the Al foil falls within the range of 930-940 cm-1, a high capacitance can be achieved, because the homogeneity of the coating film is secured and the film can be electrolytically etched easily.
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