Protection film structure for functional devices

Claim 1

A protection film structure for protecting a functional device from water comprising: a substrate body having two opposite sides; a protection film covering one said side of said substrate body and being secured thereto via a layer of bonding film; said substrate body being made of a material selected from the group consisting of acrylate polystyrene, dehydrated polycarbonate, polyethylene, polyester, polyvinylchloride; said protection film being an inorganic film containing silicon and nitride atoms, not necessarily in a stoichiometric proportion equivalent to silicon nitride; said substrate body and said protection film having different coefficients of thermal expansion relative to one another; a humidity-sensitive functional device having a front side mounted on said protection film; said functional device being constituted by at least one of a photosensor film, a semiconductor, an electronics component, an optical disk, an optomagneto memory sheet, a magnetic recording tape, an optoelectronic sensing array, and a recording film having recording grooves and made of at least one of TeO x and TeC; said bonding film being formed between said substrate body and said protection film and having a hardness which is smaller than that of said protection film; said bonding film being arranged to release stress due to difference in thermal expansion coefficients between said substrate body and said protection film; said bonding film including at least one buffer layer made of at least one oxide selected from the group consisting of silicond oxide, tin oxide, indium oxide, lead oxide and titanium oxide, said bond film being in the range of 1.0 to 10 μm thick; and a passivation film protecting a rear side of said functional device, said passivation film being formed on said protection film in a manner to cover said rear side of said functional device.