A substrate including a self-supporting tri-layer stack is described. The tri-layer stack includes first and second outer layers and a biaxially oriented layer disposed between and in direct contact with the first and second outer layers. The biaxially oriented layer may include a first polyester having greater than 45 mole percent naphthalate units and greater than 45 mole percent ethylene units. Each of the first and second outer layers includes a second polyester which may include 40 to 50 mole percent naphthalate units, at least 25 mole percent ethylene units, and 10 to 25 mole percent of branched or cyclic C4-C10 alkyl units.