Patent ID: 8912427

Claim:
A polyester film for sealing a backside of a solar cell, wherein the polyester film has a light reflectance at 550 nm wavelength of 50% or more, contains 3 to 50% by mass of inorganic fine particles, has an acid value of 1 to 30 eq/ton, has an in-face variation of light reflectance to a mean value of light reflectance of 5% or less, and has a limiting viscosity of 0.60 to 0.80 dL/g, wherein the film is obtained by preparing a master batch comprising a polyester resin and inorganic fine particles; subjecting the master batch to solid-phase polymerization; and, after that, forming a mixture by pouring a polyester resin containing no inorganic fine particles and the master batch into an extruder and melt extruding the mixture, wherein a difference between a limiting viscosity of the master batch and a limiting viscosity of the polyester resin to be mixed therewith is 0.15 dL/g or less.