TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Process: The gas barrier layer and the planarization layer are repeatedly laminated several times. The gas barrier layer is formed by vapor deposition of an inorganic oxide or inorganic nitride chosen from silicon oxide, silicon nitride and aluminum oxide. The planarization layer is formed using a composition containing a metal alkoxide and/or hydrolyzed substance, and solvent soluble property polymer, by sol gel method. Preferred Component: The metal alkoxide having functional group contains nitrogen, oxygen, sulfur and halogen. The planarization layer is formed by performing ultraviolet irradiation of the composition by heating. Low-temperature plasma processing and/or anchor coat processing are performed to gas barrier layer-lamination layer surface of the base film.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Process: The gas barrier layer and the planarization layer are repeatedly laminated several times. The gas barrier layer is formed by vapor deposition of an inorganic oxide or inorganic nitride chosen from silicon oxide, silicon nitride and aluminum oxide. The planarization layer is formed using a composition containing a metal alkoxide and/or hydrolyzed substance, and solvent soluble property polymer, by sol gel method. Preferred Component: The metal alkoxide having functional group contains nitrogen, oxygen, sulfur and halogen. The planarization layer is formed by performing ultraviolet irradiation of the composition by heating. Low-temperature plasma processing and/or anchor coat processing are performed to gas barrier layer-lamination layer surface of the base film.    TECHNOLOGY FOCUS - POLYMERS - Preferred Property: The base film has linear expansion coefficient of 5-15 ppm/degreesC, and contains glass fiber, glass flakes and polyethylene naphthalate as base material polymer. The refractive index difference of base material polymer with glass fiber and glass flakes is 0.01 or less. EXAMPLE - A polyethylene naphthalate film having thickness of 25 microns and linear expansion coefficient of 13 ppm/degreesC was used as base film. A gas barrier layer having thickness of 100 nm was formed by vapor depositing silicon oxide having oxidation degree of 1.8. The gas barrier layer was laminated on one surface of base film by sputtering method. 1 g/m2 of planarization layer formation composition containing tetraethoxy silane (in mass parts) (34), water (15), isopropyl alcohol (10), tertiary amine (0.17) and gamma-glycidoxy propyl trimethoxysilane (3.4) was coated on the outer surface of gas barrier layer, and heated at 120degreesC for 1 minute. Thus, high-barrier sheet was obtained. The sheet had water vapor permeability of 0.3 g/m2.24 hours measured at 40degreesC and 90% relative humidity according to JIS-Z-0208B.