Silica and silica/polymethylmethacrylate (PMMA) hybrid thin films 0.15-0.9 μm in thickness were deposited on polybutyleneterephthalate (PBT) substrates by dip-coating followed by heat-treatment at 170° or 180°C, using perhydropolysilazane (PHPS) and tetraethylorthosilicate (TEOS) as a silica source. A contamination test was carried out using curry as a contaminant; the curry was placed on the thin film samples, heated at 150°C, and then removed with neutral detergent, followed by microscopic observation and color difference measurement. Coating with silica either using TEOS or PHPS was effective in suppressing the contamination, where the latter was found to be more effective than the former. Although the as-prepared silica and silica/PMMA hybrid thin films were crack-free, the films tended to be cracked when subjected to the contamination test, which was more significant for those prepared at higher substrate withdrawal speeds. The cracking tendency, however, was found to decrease when silica was hybridized with PMMA, and no cracks were observed on the contamination test for the sample prepared at PMMA/PHPS mass ratios higher than 1.2. The degree of contamination was minimized at a PMMA/PHPS mass ratio of 0.8, where excellent adhesion was also found between the film and the substrate.
