| 摘要 |
PROBLEM TO BE SOLVED: To provide a copolyester and a polyester composition using the copolyester, for achieving such a property that in an optical polyester film as a laminate of a high refractive index layer and a low refractive index layer, edge chips produced in a process of forming a film can be recovered.SOLUTION: The copolyester comprises: an acid component comprising 50 to 70 mol% of a 2,6-naphthalene dicarboxylic acid component and 30 to 50 mol% of a cyclohexane dicarboxylic acid component; and a glycol component comprising 30 to 50 mol% of an ethylene glycol component and 50 to 70 mol% of a spiroglycol component. The copolyester has an average refractive index in the range from 1.540 to 1.560. The polyester composition is obtained by melting and kneading an ethylene naphthalate resin having an average refractive index of 1.630 or more and the above copolyester, in a weight ratio of (35 to 50):(65 to 50), and the composition has an average refractive index in the range from 1.580 to 1.590. |
