Flame-retardant biaxially-oriented polyester film

A reflective film comprising a flame-retardant biaxially-oriented polyester film comprising:

• a polymer component containing polyethylene terephthalate;
• and
• a flame retardant,
• wherein
• the polyester film has an intrinsic viscosity of 0.50 to 0.64 dL/g and a density of 1.21 to 1.27 g/cm3,
• a content of the polyethylene terephthalate in the polyester film is 70 to 97% by mass,
• the flame retardant contains at least one phosphorus-based flame retardant selected from the group consisting of a phosphinate represented by general formula (1) below and a diphosphinate represented by general formula (2) below,
• a content of the phosphorus-based flame retardant in the polyester film is 3 to 8% by mass,
• the polyester film is a porous film having an average reflectance of 60 to 74% at a wavelength of 400 to 700 nm, and
• the polyester film has a thickness of 15 to 45 μm:
• wherein R1 and R2 are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, or an aryl group, M represents a metal, and m represents a valence of M, and
• wherein R3 and R4 each independently represent hydrogen, an alkyl group having 1 to 6 carbon atoms, or an aryl group, R5 represents an alkylene group having 1 to 6 carbon atoms, an arylene group having 6 to 10 carbon atoms, an alkylarylene group, or an arylalkylene group, M represents a metal, and n represents a valence of M.