The invention relates to 1,6,9,14-tetrasubstituted terrylene tetracarboxylic acid diimides of general formula (I), in which the variables are defined as follows: X, Y independently of one another represent bromium; cyano; aryloxy, arylthio, hetaryloxy or hetarylthio, which can respectively be mono- or polysubstituted by C1-C12 alkyl, C1-C12 alkoxy, —COOR1, —SO3R1, halogen, hydroxy, carboxy, cyano, —CONHR2 and/or —NHCOR2; a group of formula -L-R3; a group of formula —NR22; R, R′ independently of one another represent hydrogen; C1-C30 alkyl, whose carbon chain can be interrupted by one or more groupings —O—, —S—, —NR1—, —CO— and/or —SO2— and which can be mono- or polysubstituted by cyano, C1-C6 alkoxy, aryl, which may be substituted by C1-C18 alkyl or C1-C6 alkoxy and/or a 5- to 7-membered heterocyclic group that is bonded by means of a nitrogen atom and that can contain additional heteroatoms and be aromatic; C5-C8 cycloalkyl, whose carbon skeleton can be interrupted by one or more groupings —O—, —S— and/or —NR1— and/or which can be mono- or polysubstituted by C1-C6 alkyl; aryl or hetaryl, which can be mono- or polysubstituted by C1-C18 alkyl, C1-C6 alkoxy, cyano, —CONHR2, —NHCOR2 and/or aryl- or hetarylazo, which can be respectively substituted by C1-C10 alkyl, C1-C6 alkoxy or cyano; and L represents 1,2-ethylene, 1,2-ethenylene or 1,2-ethynylene.