Biaxially stretched laminated polyester film, infrared light shielding structure for laminated glass composed of the same, and laminated glass composed of the same

A biaxially stretched laminated polyester film comprising 51 layers or more in total, in which a first layer and a second layer are alternately laminated, which is characterized in that a polyester (A) constituting the first layer is polyethylene-2,6-naphthalenedicarboxylate;

• a polyester (B) constituting the second layer is a polyester containing at least one of an ethylene terephthalate component and an ethylene naphthalene dicarboxylate component;
• an average reflectance within a wavelength range of 400 to 750 nm is not more than 25%;
• an average reflectance within a wavelength range of 800 to 1,200 nm is 50% or more;
• and a Young's modulus of the film at 90° C. is 2,400 MPa or more in at least one direction of the longitudinal direction and the lateral direction of the film,
• wherein the biaxially stretched laminated polyester film has a single-layered protective layer composed of a polymer having a glass transition temperature of 90° C. or higher and having a thickness of 5 μm or more and not more than 20 μm on both sides of a laminated structure portion (I) in which the first layer and the second layer are alternately laminated,
• wherein the single-layered protective layer and the laminated structure portion (I) are directly attached,
• wherein the polymer of the protective layer includes polyethylene naphthalate, polystyrene, polyphenylene sulfide, polyether sulfone, or polyphenylene oxide.