Separately, a mixture (composition 1) of an electron-beam-curable unsaturated organic compound of the formula (I) in which R is a methyl group and the sum of a, b and c is 3, namely tri-PO-modified trimethylolpropane triacrylate, an electron-beam-curable unsaturated organic compound of the formula (II) in which R is a hydrogen atom and the sum of a', b' and c' is 6, namely hexa-EO-modified trimeth