High durable mold fabricated with hot-embossing a sol-gel derived organically modified silicate film

A high durable and low-cost mold was fabricated with hot-embossing a sol-gel derived organically modified silicate film using a commercially available grating as a mother mold. Close pattern transfer from the mother mold to the film (daughter mold) was confirmed. The thermooptic coefficient of the daughter mold was measured and found to be unchanged during 9 times heating and cooling cycle. This result implies that the mold has no residual stress and so leads to fine patterning in embossing process. We hot-embossed polymethyl methacrylate (PMMA) films not with the expensive mother mold, but with the daughter mold. More than thirty PMMA grating replicas could be successively fabricated using one daughter mold without cleaning and treating the surface. This is due to the hydrophobicity of the daughter mold. After heating at 250°C for 120 hours, the water contact angle was approximately above 90°, and so the daughter mold did not lose its hydrophobicity. Because of the hydrophobicity, no significant problem that the daughter mold stuck to the PMMA film was observed for the successive embossing. It was confirmed with AFM observation that there was no difference in pattern dimension between the daughter mold and PMMA replicas. Hence, the daughter mold is high durable. Moreover, we measured the transmitted diffraction light power of the fabricated PMMA gratings, and found that there was no difference in the diffraction efficiency of the gratings. Therefore, the daughter mold is suitable for low-cost hot embossing of polymer materials.