3 propylene terephthalate poly cyclohexanedimethanol terephthalate poly cyclohexanedimethanol co ethylene terephthalate poly ethylene naphthalate poly butylene naphthalate and polyarylates in another embodiment the substrate layer comprises a thermoplastic elastomeric polyesters tpe 39 s as defined herein a thermoplastic elastomer is a material that can be processed as a thermoplastic material but which also possesses some of the properties of a conventional thermoset resin suitable examples of thermoplastic elastomeric polyesters include but are not limited to polyetheresters poly alkylene terephthalate poly ethylene terephthalate poly butylene terephthalate polyetheresters containing soft block segments of poly alkylene oxide particularly segments of poly ethylene oxide and poly butylene oxide polyesteramides such as those synthesized by the condensation of an aromatic diisocyanate with dicarboxylic acids and any polyester with a carboxylic acid terminal group optionally the substrate layer can further comprise at least one dielectric layer at least one insulating layer or any combinations thereof the dielectric layer s which are often employed as heat controllers typically have a thickness between about 200 u00e5 and about 1 000 u00e5 suitable dielectric layers include but are not limited to a nitride layer e g silicone nitride aluminum nitride an oxide layer e g aluminum oxide a carbide layer e g silicon carbide and any combinations comprising at least one of the foregoing and any compatible material that is not reactive with the surrounding layers in the context of the present disclosure a typical data storage medium further comprises at least one data layer part 30 in fig1 part 80 in fig2 the data layer which typically comprises a reflective metal layer.