A primer composition suitable for priming for a polysiloxane outer coat, comprising vinyl polymer having hydrolysable silyl groups and/or SiOH groups and organic UV-absorbing groups attached to side chains, and organopolysiloxane of the general formula: a Si b O (4-a-b)/2 wherein each R independently is a substituted or unsubstituted monovalent hydrocarbon group of 1 to 18 carbon atoms excluding amino-containing monovalent hydrocarbon groups, being selected from alkyl, aryl, haloalkyl, haloaryl, alkenyl, substituted forms of the foregoing in which one or more hydrogen atoms are replaced by epoxy, (meth)acryloxy or mercapto group, and wherein the hydrocarbon group may be interrupted by O or S, each Y independently is hydroxyl group, alkoxy group of 1 to 3 carbon atoms, alkoxyalkoxy group of 2 to 4 carbon atoms, acyloxy group of 1 to 6 carbon atoms, alkenoxy group of 1 to 6 carbon atoms, or isocyanate group, the subscripts "a" and "b" are numbers satisfying 0 < a < 2, 0 < b < 3 and 0 < a+b < 4, the amounts of component being from 0.1 to 100 parts by weight solids per 100 parts by weight of; said primer composition being curable to form a layer having a coefficient of linear expansion equal to or less than 150x10 -6 /°C. vinyl polymer having hydrolysable silyl groups and/or SiOH groups and organic UV-absorbing groups attached to side chains, and organopolysiloxane of the general formula: a Si b O (4-a-b)/2 wherein each R independently is a substituted or unsubstituted monovalent hydrocarbon group of 1 to 18 carbon atoms excluding amino-containing monovalent hydrocarbon groups, being selected from alkyl, aryl, haloalkyl, haloaryl, alkenyl, substituted forms of the foregoing in which one or more hydrogen atoms are replaced by epoxy, (meth)acryloxy or mercapto group, and wherein the hydrocarbon group may be interrupted by O or S, each Y independently is hydroxyl group, alkoxy group of 1 to 3 carbon atoms, alkoxyalkoxy group of 2 to 4 carbon atoms, acyloxy group of 1 to 6 carbon atoms, alkenoxy group of 1 to 6 carbon atoms, or isocyanate group, the subscripts "a" and "b" are numbers satisfying 0 < a < 2, 0 < b < 3 and 0 < a+b < 4, the amounts of component being from 0.1 to 100 parts by weight solids per 100 parts by weight of; said primer composition being curable to form a layer having a coefficient of linear expansion equal to or less than 150x10 -6 /°C. each R independently is a substituted or unsubstituted monovalent hydrocarbon group of 1 to 18 carbon atoms excluding amino-containing monovalent hydrocarbon groups, being selected from alkyl, aryl, haloalkyl, haloaryl, alkenyl, substituted forms of the foregoing in which one or more hydrogen atoms are replaced by epoxy, (meth)acryloxy or mercapto group, and wherein the hydrocarbon group may be interrupted by O or S, each Y independently is hydroxyl group, alkoxy group of 1 to 3 carbon atoms, alkoxyalkoxy group of 2 to 4 carbon atoms, acyloxy group of 1 to 6 carbon atoms, alkenoxy group of 1 to 6 carbon atoms, or isocyanate group, the subscripts "a" and "b" are numbers satisfying 0 < a < 2, 0 < b < 3 and 0 < a+b < 4, the amounts of component being from 0.1 to 100 parts by weight solids per 100 parts by weight of; said primer composition being curable to form a layer having a coefficient of linear expansion equal to or less than 150x10 -6 /°C.