Photo Etching of Polyimide Thin Film by TiO 2 Micro Wire Prepared Using Phase Separation-Selective Leaching Method
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Photo Etching of Polyimide Thin Film by TiO2 Micro Wire Prepared Using Phase Separation-Selective Leaching Method
Y. Sone, K. Nishio and A. Yasumori Department of Materials Science and Technology, Tokyo University of Science 2641 Yamazaki, Noda-shi, Chiba 278-8510 Japan
ABSTRACT TiO2 photocatalysts have a strong oxidation ability for organic compounds under UV irradiation. The surfaces of polyimide and polymethyl methacrylate (PMMA) were photocatalytically machined using a porous TiO2 wire prepared by phase separation and selective leaching with elongation. After UV irradiation, these surfaces were decomposed along the length of the TiO2 wire. Such surface decomposition depended on the irradiation angle of UV light and irradiation time. The machining rate of PMMA was higher than that of the polyimide. INTRODUCTION TiO2 is a typical semiconductor photocatalyst, that decomposes organic substances under UV light irradiation at a strong oxidizing power, because of its induction of various oxygen radicals [1-6]. Therefore, TiO2 photocatalysts are useful in deodorization, antibacterial processes, sterilization, and antifouling [7-8]. Furthermore, they exhibit super-hydrophilicity, which applies to self-cleaning [9-10]. Diamond, diamond-like carbon (DLC) and polyimide are attractive materials for light-emitting devices or are used as protective films for high-capacity memory media. However, for practical use, their high-resolution machining and the smoothing of their surface are necessary. However, they are so mechanically hard and chemically inactive that it is not easy to machine their surface by conventional chemical or physical processes. Recently, TiO2 has been applied to the surface modification of such materials, for example, the photodecomposition of the surface of SiC single crystals by oxidizing them to SiO2 , the photopatterning of self-assembled monolayers (SAMs), and the photomachining of the surface of silicon or copper metal plates using photomasks [11-12]. These techniques for surface modification using a TiO2 photocatalyst have various advantages as follows: damage to target substrates is very little because the light source used is UV light of relatively long wavelength, and they require no special conditions or equipment, such as an ultrahigh-vacuum atmosphere and a high-power electron, ion or laser beam. Yasumori et al. reported the preparation of a porous TiO2 photocatalyst by the phase separation of two liquid melts followed by selective leaching in the TiO2-SiO2 system; the photocatalyst shows a higher photocatalytic activity than P-25 and generates hydrogen through dehydrogenation from an aqueous methanol solution under UV light irradiation [13]. Such the preparation has the advantage that it can be used to prepare wirelike materials by a drawing technique because it involves high-temperature melting and quenching. In this study, a porous TiO2 wire was prepared by phase separation followed by selective leaching, and the local modification of the surface of chemically inactive polyimide t
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