Patent ID: 8609255

Claim:
A polyester film having a laminate structure comprising a polyester layer (layer P 1 ) containing a crystalline polyester and inorganic particles and a polyester layer (layer P 2 ) containing a crystalline polyester, inorganic particles, and an antihydrolysis segment, wherein content Wa 2 of the inorganic particles in the layer P 2 is at least 10 mass % of the layer P 2 , a difference between content Wa 2 (mass %) of the inorganic particles in the layer P 2 and content Wa 1 (mass %) of the inorganic particles in the layer P 1 , Wa 2 -Wa 1 , is 5 to 25 mass %, content Wb 2 of the antihydrolysis segment in the layer P 2 is 0.02 to 1.5 mass % of the layer P 2 , and a ratio T 1 /T 2 between layer thickness T 1 (μm) of the layer P 1 and layer thickness T 2 (μm) of the layer P 2 is 2 to 15.