Patent ID: 8394457

Claim:
A method for the preparation of a porous thin film comprising the steps of: applying, onto a surface of a substrate, a solution of a precursor composition for forming a porous thin film prepared by blending, in an organic solvent, at least one member selected from the group consisting of compounds (A) represented by the following general formula (1) and compounds (B) represented by the following general formula (2): Si(OR 1 ) 4 (1) R a (Si)(OR 2 ) 4−a (2) wherein in the foregoing formulas (1) and (2), R 1 represents a monovalent organic group; R represents a hydrogen atom, a fluorine atom or a monovalent organic group; R 2 represents a monovalent organic group; and a is an integer ranging from 1 to 3, provided that R, R 1 and R 2 may be the same or different from one another; a heat decomposable organic compound (C) which undergoes heat decomposition at a temperature of not less than 250° C.; and at least one component (D) which is at least one element selected from the group consisting of amphoteric elements having an electronegativity of not higher than 2.5, elements having an ionic radius of not less than 1.6 Å and elements having an atomic weight of not less than 130, or is at least one compound containing at least one element selected from the group consisting of amphoteric elements having an electronegativity of not higher than 2.5, elements having an ionic radius of not less than 1.6 Å and elements having an atomic weight of not less than 130; and then mixing the resulting mixed solution with a compound (E) which is thermally decomposed at a temperature ranging from 90 to 200° C. and can generate an amine through the thermal decomposition and whose aqueous solution and/or solution in an alcohol/water mixed solvent have a pH value falling within the range of from 6.5 to 8, at a temperature of not higher than the heat-decomposition temperature thereof; drying a resulting coated layer of the solution by heating the same at a temperature ranging from 100 to 400° C.; irradiating a porous thin film formed on the substrate surface with ultraviolet rays having a wavelength ranging from 157 to 344 nm; and then; reacting the porous thin film with a hydrophobic compound having a hydrophobic group and at least one group selected from polymerizable groups through a gas-phase reaction carried out at a temperature ranging from 100 to 600° C. to thus form a hydrophobic porous thin film.