RETARDATION FILM, PRODUCTION METHOD OF THE SAME, AND POLARIZING PLATE

摘要

PROBLEM TO BE SOLVED: To provide a retardation film which is stretched in a high magnification and can achieve a high retardation even when a total substitution degree of a hydroxy acid-modified glucan derivative is large.SOLUTION: The retardation film comprises a hydroxy acid-modified glucan derivative in which a hydroxy acid component is graft-polymerized to a hydroxyl group of a glucan derivative, wherein an average substitution degree of a graft chain of the hydroxy acid component is controlled to 0.1 or more, an average polymerization degree of the graft chain of the hydroxy acid component is controlled to 7 or more, and an average 1 mol or more of the hydroxy acid component in terms of a hydroxy acid is grafted to 1 mol of the glucose unit of the glucan derivative. The glucan derivative may be a cellulose acylate; and the total of an average substitution degree of an acyl group and an average substitution degree of the graft chain of the hydroxy acid component may be 2.4 or more. The hydroxy acid component may be a lactone having 4 to 10 carbon atoms. The retardation film may be a film stretched in a stretch magnification of over 1 and 3.5 or less.