The invention relates to an adhesive. Provision is made for the adhesive to comprise (a) 50 to 95% by weight of a heat-activable or pressure-sensitively adhesive polymer formed from a comonomer mixture comprising, based on the polymer, (a1) 40 to 95% by weight of acrylic and/or methacrylic esters of the formula CH.sub.2.dbd.CH(R.sub.1)(COOR.sub.2), where R.sub.1 is H and/or CH.sub.3 and R.sub.2 is H and/or alkyl chains having 1 to 30 carbon atoms; (a2) 5 to 30% by weight of a first copolymerizable vinyl monomer containing at least one carboxylic and/or sulphonic and/or phosphonic acid group; (a3) 1 to 10% by weight of a second copolymerizable vinyl monomer containing at least one epoxy group or one acid anhydride function; and (a4) 0 to 20% by weight of a third copolymerizable vinyl monomer containing at least one functional group which differs from the functional group of the first copolymerizable vinyl monomer and from the functional group of the second copolymerizable vinyl monomer; and also (b) 5 to 50% by weight of an epoxy resin or a mixture of two or more epoxy resins.