Advanced Organic-inorganic Hybrid Coatings Having Both High Gas Barrier Properties and Abrasion Resistance
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0951-E12-32
Advanced Organic-Inorganic Hybrid Coatings Having Both High Gas Barrier Properties and Abrasion Resistance Katsunori Nishiura1, Toshihiko Takaki1, and Makoto Nakaura2 1 Material Science Laboratory, Mitsui Chemicals, Inc., 580-32 Nagaura, Sodegaura, Chiba, 2990265, Japan 2 Mitsui Chemical Analysis & Consulting Service Inc., 580-32 Nagaura, Sodegaura, Chiba, 2990265, Japan
ABSTRACT It is important to develop flexible transparent polymer films having high gas barrier properties and abrasion resistance because new applications involving transparent polymer films for flat panel displays require these properties. We report on organic-inorganic hybrid coatings of polyvinylalcohol (PVA)/polyacrylicacid (PAA)-silica, which have high abrasion resistance and high gas barrier properties almost equivalent to those achieved by the dry coating process. The hybrid coatings were prepared by the sol-gel reaction of alkoxysilane in a PVA/PAA aqueous solution. In order to obtain transparent coating films, 3-aminopropyltrimethoxysilane (APTMOS) was used as a compatibilizer in the sol-gel reaction of tetramethoxysilane (TMOS). No structure could be seen in the TEM of the cross-sectional coating layer, indicating that polymers and silica were mixed homogeneously. PVA/PAA-silica hybrid coatings were shown to have excellent abrasion resistance based on the ∆Haze index. O2 permeability of PVA/PAAsilica hybrid coatings evaluated by MOCON under the conditions of 23°C, 90% RH was lower than that of PVA/PAA polymer coating, which suggests that silica affects the barrier property of the hybrid coating in humid conditions. Furthermore, O2 permeability decreased as silica content increased in the coatings. Unexpectedly, high gas barrier properties appeared when the silica content exceeded 50 wt%. From the result of element distribution analysis measured by EFTEM, it was confirmed that phase separation occurred between PVA/PAA and silica on a nanometer scale and silica forms continuous structures, which are considered to suppress O2 permeability. INTRODUCTION Transparent polymers are widely used for many applications such as package films, plastic lenses, and substrates for optical displays. The advantages of transparent polymer films are that they are flexible, lightweight and easy to process compared to glass. On the other hand, the disadvantages of polymer films are low gas barrier properties and low abrasion resistance. Therefore, hard coatings and gas barrier coatings are required for the transparent polymer film to satisfy the demands for new applications. The traditional method of providing high gas barrier properties for polymer films is the wellknown dry coating process, in which the surface of polymer films is coated by vapor deposition of metal oxides such as SiO2 or Al2O3. Although dry coating can give polymer films high gas barrier properties, abrasion resistance is not improved by this method. Therefore, if the dry coating process is used, a hard coating must still be formed by a wet coating process to protect the polyme
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