Highly concentrated ozone gas, of greater than 20%, was applied, for the first time, in order to obtain a stable wettable polyimide film surface. The water contact angle of the polyimide film surface decreased from 60 to nearly 20 after exposure to the highly concentrated ozone gas. The increase in the small water contact angle during storage in ambient air was very gradual, i.e., 5 for over one month. Scanning electron microscopy and the atomic force microscope showed that surface roughening simultaneously occurred. Since the X-ray photoelectron spectra showed an increase in oxygen concentration at the polyimide film surface, the highly concentrated ozone gas is considered to produce a wettable surface by the significant oxidation of the polyimide film chains on the surface.

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