| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical film excellent in transparency, toughness and moisture permeability, having a low photoelastic coefficient and capable of inhibiting the formation of optical birefringence by heating, and a retardation film and polarizing plate by using the same. SOLUTION: This optical film is provided by containing a polyvinyl acetal resin having a constituting unit expressed by formula (1), and having≥130°C glass transition point of the polyvinyl alcohol and also 30 to 80 mol% content of the constituting unit expressed by formula (1) in the polyvinyl acetal resin. COPYRIGHT: (C)2008,JPO&INPIT
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