. . . . "A is O or S; x is O or 1; Ar is a group or Ar is cyclopentyl, cyclohexyl, naphthyl, anthracyl, biphenylyl or an O-, S- or N-containing 5- or 6-membered heterocyclic ring, where the radicals cyclopentyl, cyclohexyl, naphthyl, anthracyl, biphenylyl and 5- or 6-membered heterocyclic ring are unsubstituted or substituted by halogen, C1-C4alkyl and/or C1-C4alkoxy;" . .