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, -COOR , -SO3R , halogen, hydroxy, carboxy, cyano, -CONHR and/or -NHCOR ; a group of formula -L-R ; a group of formula -NR 2; 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 -NR - 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, -CONHR , -NHCOR 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.