NOVELTY - A back surface protection sheet (6) comprises a thermal-diffusion layer (61), a weather-proofing layer (62) and a thermal radiation layer (63) laminated on a base material layer (60). The heat conductivity of the thermal-diffusion layer is 150 W/(m K). The weather-proofing layer has a mechanical strength maintenance factor of 50% or more. The thermal-diffusion layer and the thermal radiation layer are laminated using resin containing hydrolysis-resistant polyethylene terephthalate, modified polyphenylene ether, or a polycarbonate.    USE - Back surface protection sheet is used for solar cell module (claimed) for outdoor.    ADVANTAGE - The back surface protection sheet has excellent durability, prevents the decline of generating efficiency, and suppresses the raise of inside temperature of solar cell module.    DETAILED DESCRIPTION - A back surface protection sheet comprises a thermal-diffusion layer, a weather-proofing layer and a thermal radiation layer laminated on a base material layer. The heat conductivity of the thermal-diffusion layer is 150 W/(m K). The weather-proofing layer has mechanical strength maintenance factor of 50% or more measured by endurance test for 2000 hours at 85 degrees C and 85% RH based on JIS C8917. The thermal-diffusion layer and the thermal radiation layer are laminated using resin containing hydrolysis-resistant polyethylene terephthalate, modified polyphenylene ether, or polycarbonate. The thermal radiation layer comprises resin containing far-infrared radiation filler, and thermal emissivity more than weather-proofing layer, and is laminated on the outermost layer of the back surface protection sheet. An INDEPENDENT CLAIM is included for solar cell module, which comprises the back surface protection sheet, sealing material sheet, solar cell element laminated, in which the thermal radiation layer of the back surface protection sheet is positioned in outermost layer of the solar cell module.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of back protection sheet of solar cell module.    Back surface protection sheet (6)    Base material layer (60)    Thermal diffusion layer (61)    Weather proofing layer (62)    Thermal radiation layer (63)