NOVELTY - A solar cell back surface protection sheet consists of adhesive layer, outer layer substrate, middle layer substrate, and an inner layer substrate adhered by adhesive (BB) containing component including linear polyester polyol, polyester polyurethane polyol, and bisphenol-type epoxy resin. The linear polyester polyol is obtained by reacting dibasic acid component containing aromatic dibasic acid, and dihydric alcohol component. The polyester polyurethane polyol is obtained by reacting dibasic acid component containing aromatic dibasic acid and dihydric alcohol component.    USE - Solar cell back surface protection sheet is used for solar cell module (claimed) for photovoltaic power generation.    ADVANTAGE - The solar cell back surface protection sheet has excellent durability, reliability, moist-heat resistance, and adhesiveness at low temperature environment, and is economical.    DETAILED DESCRIPTION - A solar cell back surface protection sheet consists of adhesive layer which bonds to surface(s) of thick outer layer substrate having weather resistance, middle layer substrate, and an inner layer substrate adhered by means of adhesive containing main component including linear polyester polyol of specific configuration, polyester polyurethane polyol, bisphenol-type epoxy resin, and curing agent containing polyisocyanate. The adhesive contains 4-12 parts weight of solid content of curing agent with respect to 100 parts weight of solid content of main component. The linear polyester polyol is obtained by reacting dibasic acid component containing 40-70 mol% of aromatic dibasic acid and 30-60 mol% of 9-10C aliphatic dibasic acid, and dihydric alcohol component containing 30-40 mol% of 5C or more aliphatic dihydric alcohol. The linear polyester polyol has weight average molecular weight of 70000-80000. The polyester polyurethane polyol is obtained by reacting dibasic acid component containing 60-80 mol% of aromatic dibasic acid and 20-40 mol% of 9-10C aliphatic dibasic acid, and dihydric alcohol component containing 70-80 mol% of 5C or more aliphatic dihydric alcohol. The polyester polyurethane polyol has weight average molecular weight of 30000-40000. The bisphenol-type epoxy resin has number average molecular weight of 1000-2000. The polyisocyanate has isocyanurate of isophorone diisocyanate. The inner layer substrate is used as sealing material for sealing electricity generating element used for solar cell module.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of laminated structure of solar cell back surface protection sheet. (Drawing includes non-English language text)    Low-density polyethylene film (AA)    Adhesive (BB)    Polyethylene terephthalate film (CC)    Weather-resistance film (DD)