| abstract |
A polyester film to seal the back of a solar cell that has a light reflectance at 550 nm wavelength of 50% or more and that contains 3 to 50% by mass of inorganic fine particles, characterized by the acid value of the film is 1 to 30 eq / ton and the limiting viscosity of the film is 0.60 to 0.80 dL / g, and because the variation in the face of the light reflectance at the average value of the light reflectance is 5 % or less, where the light reflectance is determined as described in the description, where the acid value is determined by dissolving samples of the film for 3, 5 and 7 minutes, respectively, in benzyl alcohol, titrating with KOH solution 0 , 04 mol / l and determining the acid value from the amount valued for a dissolution time of 0 minutes, calculated by means of a method of least squares, and where the limiting viscosity is determined by preparing a solution of the film icle with a concentration of 0.4 g / dl in a mixed solvent of phenol and tetrachloroethane at a weight ratio of 60/40, determining the viscosity of the solution and the solvent using a Ubbelohde viscometer, and calculating the limiting viscosity using Huggin's formula with a Huggin constant of 0.38. |