The invention concerns a primer comprising a mixture G, in dispersion or solution in one or more solvents, of at least one copolymer obtained by copolymerizing a monomer mixture comprising at least 90 wt% of the following monomers: vinylcaprolactam and/or vinylpyrrolidone and one or more of monomers a) and/or b): a) acrylic esters of a linear, primary alcohol having 2 to 10 carbon atoms in the alkyl radical of the alcohol, b) acrylic esters of a branched non-cyclic alcohol having 3 to 12 carbon atoms in the alkyl radical of the alcohol, at least one organofunctional silane of the general structure (I): (R
1 O-)
x Si(R
2 )
y (R
3 )
z , in which the radicals R
1 independently of one another are a C
1 -C
4 alkyl radical, a C
2 -C
6 alkoxyalkyl radical or an acetyl radical; the radical R
2 is an aminoalkyl radical, a vinyl group, a methacryloyloxyalkyl radical, an isocyanatoalkyl radical, an O-methylcarbamatoalkyl radical, a glycidoxyalkyl radical or a phenyl radical; the radicals R
3 independently of one another are a C
1 -C
18 alkyl radical and x = 1, 2 or 3; y = 0 or 1 and z = 4 –x –y; at least one metal compound selected from the group consisting of metal acetylacetonates, metal alkoxides and alkoxy-metal acetylacetonates. A primer of this kind enables effective promotion of adhesion between pressure-sensitive adhesive tapes and hydrophilic surfaces like glass especially, and allows for incorporation of functional fillers.