A coating composition primarily comprising a disilane compound of the formula (A): X.sub.mR.sup.1.sub.3-mSi--Y--SiR.sup.1.sub.3-mX.sub.m (A) wherein R.sup.1 is a monovalent hydrocarbon group, Y is a divalent fluorinated organo group, X is a hydrolyzable group, and m is 1, 2 or 3, or a (partial) hydrolyzate thereof is applied and cured to form a protective coat having excellent chemical resistance and antireflection.