| abstract |
[Problem] In order to provide a folding-type display having excellent mass producibility and having no risk of distortions arising in an image displayed in a folding section after having been bent repeatedly, the invention provides a polyester film for use in a folding-type display touch panel module base material, wherein no cracks occur in the folding section. [Solution] The polyester film for use in the folding-type display touch panel module base material satisfies the following conditions: (1) the refractive index in the bending direction is 1.590 to 1.620, (2) the refractive index in the direction of the folding section is 1.670 to 1.700, (3) the refractive index in the thickness direction is 1.520 or lower, and (4) the density is 1.380 g/cm3 or greater. (Herein, the bending direction is a direction that is orthogonal to the folding section when folding the polyester film.) |