using the langmuir - blodgett &# 39 ; s technique and a compound represented by the general formula cf 3 n m -- x , wherein x is a hydrophilic group , preferably -- cooh , n is from 5 to 20 and m is from 0 to 10 , a firm built - up film having a desired number of monomolecular layers can surely be formed on a solid substrate surface by spreading a monomolecular film of the fluorinated compound on an aqueous phase containing trivalent metal ions . in the obtained built - up film the cf 3 - terminated molecules are well oriented in the direction of the thickness of the film . the built - up film fully exhibits extreme hydrophobicity , high insulation , low refraction and other properties characteristic of the fluorine - containing compound .