A rylenetetracarboximide of the general formula I in which the variables are defined as follows: R are identical or different radicals: hydrogen; C 1 -C 30 -alkyl whose carbon chain may be interrupted by one or more -O-, -S-, -NR 1 -, -CO- and/or -SO 2 - moieties and which may be mono- or polysubstituted by cyano, C 1 -C 6 -alkoxy, aryl which may be substituted by C 1 -C 18 -alkyl or C 1 -C 6 -alkoxy, and/or a 5- to 7-membered heterocyclic radical which is bonded via a nitrogen atom and may comprise further heteroatoms and be aromatic; C 5 -C 8 -cycloalkyl whose carbon skeleton may be interrupted by one or more -O-, -S- and/or - NR 1 - moieties and/or which may be mono- or polysubstituted by C 1 -C 18 -alkyl; aryl or hetaryl, each of which may be mono- or polysubstituted by C 1 -C 18 -alkyl, C 1 -C 18 -alkoxy, cyano, nitro, halogen, -NR 2 R 3, -CONR 2 R 3, -SO 2 R 2 and/or aryl- or hetarylazo, each of which may be substituted by C 1 -C 8 -alkyl, C 1 -C 18 -alkoxy or cyano, and to which further 5- to 7-membered saturated or unsaturated rings may be fused, which may comprise -O-, -S-, -NR 1 -, -CO- and/or -SO 2 - as ring members and/or be substituted by one or more identical or different R 2 radicals; R' are identical or different radicals: hydrogen; aryloxy, arylthio, hetaryloxy or hetarylthio, each of which may be mono- or polysubstituted by alkyl radicals R, aryl radicals R, C 1 -C 12 -alkoxy, cyano, halogen, hydroxyl, -COOR 1, - CONR 2 R 3 and/or -NHCOR 2; R 1 is hydrogen or C 1 -C 18 -alkyl; R 2, R 3 are each independently hydrogen; C 1 -C 18 -alkyl, which may be substituted by C 1 -C 6 -alkoxy, halogen, hydroxyl, carboxyl and/or cyano; aryl or hetaryl, each of which may be substituted by the aforementioned radicals specified for alkyl and by C 1 -C 6 -alkyl; n is 1 or 2. R are identical or different radicals: hydrogen; C 1 -C 30 -alkyl whose carbon chain may be interrupted by one or more -O-, -S-, -NR 1 -, -CO- and/or -SO 2 - moieties and which may be mono- or polysubstituted by cyano, C 1 -C 6 -alkoxy, aryl which may be substituted by C 1 -C 18 -alkyl or C 1 -C 6 -alkoxy, and/or a 5- to 7-membered heterocyclic radical which is bonded via a nitrogen atom and may comprise further heteroatoms and be aromatic; C 5 -C 8 -cycloalkyl whose carbon skeleton may be interrupted by one or more -O-, -S- and/or - NR 1 - moieties and/or which may be mono- or polysubstituted by C 1 -C 18 -alkyl; aryl or hetaryl, each of which may be mono- or polysubstituted by C 1 -C 18 -alkyl, C 1 -C 18 -alkoxy, cyano, nitro, halogen, -NR 2 R 3, -CONR 2 R 3, -SO 2 R 2 and/or aryl- or hetarylazo, each of which may be substituted by C 1 -C 8 -alkyl, C 1 -C 18 -alkoxy or cyano, and to which further 5- to 7-membered saturated or unsaturated rings may be fused, which may comprise -O-, -S-, -NR 1 -, -CO- and/or -SO 2 - as ring members and/or be substituted by one or more identical or different R 2 radicals; hydrogen; C 1 -C 30 -alkyl whose carbon chain may be interrupted by one or more -O-, -S-, -NR 1 -, -CO- and/or -SO 2 - moieties and which may be mono- or polysubstituted by cyano, C 1 -C 6 -alkoxy, aryl which may be substituted by C 1 -C 18 -alkyl or C 1 -C 6 -alkoxy, and/or a 5- to 7-membered heterocyclic radical which is bonded via a nitrogen atom and may comprise further heteroatoms and be aromatic; C 5 -C 8 -cycloalkyl whose carbon skeleton may be interrupted by one or more -O-, -S- and/or - NR 1 - moieties and/or which may be mono- or polysubstituted by C 1 -C 18 -alkyl; aryl or hetaryl, each of which may be mono- or polysubstituted by C 1 -C 18 -alkyl, C 1 -C 18 -alkoxy, cyano, nitro, halogen, -NR 2 R 3, -CONR 2 R 3, -SO 2 R 2 and/or aryl- or hetarylazo, each of which may be substituted by C 1 -C 8 -alkyl, C 1 -C 18 -alkoxy or cyano, and to which further 5- to 7-membered saturated or unsaturated rings may be fused, which may comprise -O-, -S-, -NR 1 -, -CO- and/or -SO 2 - as ring members and/or be substituted by one or more identical or different R 2 radicals; R' are identical or different radicals: hydrogen; aryloxy, arylthio, hetaryloxy or hetarylthio, each of which may be mono- or polysubstituted by alkyl radicals R, aryl radicals R, C 1 -C 12 -alkoxy, cyano, halogen, hydroxyl, -COOR 1, - CONR 2 R 3 and/or -NHCOR 2; hydrogen; aryloxy, arylthio, hetaryloxy or hetarylthio, each of which may be mono- or polysubstituted by alkyl radicals R, aryl radicals R, C 1 -C 12 -alkoxy, cyano, halogen, hydroxyl, -COOR 1, - CONR 2 R 3 and/or -NHCOR 2; R 1 is hydrogen or C 1 -C 18 -alkyl; R 2, R 3 are each independently hydrogen; C 1 -C 18 -alkyl, which may be substituted by C 1 -C 6 -alkoxy, halogen, hydroxyl, carboxyl and/or cyano; aryl or hetaryl, each of which may be substituted by the aforementioned radicals specified for alkyl and by C 1 -C 6 -alkyl; n is 1 or 2.