Copolymerized aromatic polyester, biaxially oriented polyester film, and magnetic recording medium

Abstract

Disclosed are a biaxially oriented polyester film which is excellent in dimensional stability, especially dimensional stability against environmental changes in, for example, temperature and humidity, and a polyester capable of providing the biaxially oriented polyester film with excellent dimensional stability. There is provided a copolymerized aromatic polyester containing aromatic dicarboxylic acid components represented by the following formulae (I) and (II) and a glycol component represented by the following formula (III), wherein a 4,4′-(alkylenedioxy)bisbenzoic acid component represented by the formula (I) is contained in an amount of 5% by mole or more and less than 90% by mole on the basis of a molar number of an aromatic dicarboxylic acid component; and a film thereof. In the structural formulae (I) to (III), RA represents an alkylene group having 1 to 10 carbon atoms; RB represents a phenylene group or a naphthalenediyl group; and RC represents an alkylene group having 2 to 4 carbon atoms or a cycloalkylene group having 8 to 10 carbon atoms.

Dependencies are inferred from the claim text.