NOVELTY - A back surface protection sheet (A) is obtained by laminating sol-gel layer (2) on surface of composite substrate (1) containing plate-shaped inorganic particles and polymer having water vapor permeability of 10 g/m2/day or less measured at 23 degrees C and relative humidity of 90% based on JIS K7126, and thickness of 10 mu m. The sol-gel layer is obtained by hardening silicon compound (I) or its hydrolyzate, organic metal compound (II) or its hydrolyzate or alkali metal polysilicate.    USE - Back surface protection sheet is used for solar cell module (claimed), liquid crystal display panel, and organic electroluminescent display panel. The gas barrier film is used for packaging bag of foodstuffs and pharmaceuticals.    ADVANTAGE - The back surface protection sheet has excellent gas barrier property, durability, dimensional stability, heat resistance and workability, and efficiently provides solar cell module having excellent performance.    DETAILED DESCRIPTION - A back surface protection sheet is obtained by laminating sol-gel layer (2) on surface of composite substrate (1) containing plate-shaped inorganic particles and polymer having water vapor permeability of 10 g/m2/day or less measured at 23 degrees C and relative humidity of 90% based on JIS K7126, and thickness of 10 mu m. The sol-gel layer is obtained by hardening silicon compound of formula: R1nSi(OX)4-n (I) or its hydrolyzate, organic metal compound of formula: M(OX)m (II) or its hydrolyzate or alkali metal polysilicate.    R1=1-12C alkyl or non-hydrolyzable and polymerizable functional group;    X=1-6C alkyl or 1-6C acyl;    M=metal atom;    n=0 or 1-3;and    m=2-4.    INDEPENDENT CLAIMS are included for the following:    (1) solar cell module, which has back surface protection sheet including sealing layer which is formed opposite to solar cell element formed on surface of transparent substrate; and    (2) gas barrier film.    DESCRIPTION OF DRAWING(S) - The drawing shows cross-sectional view of back surface protection sheet.    Composite substrate (1)    Sol-gel layer (2)    Back surface protection sheet (A)