Disclosed is the use of the compounds of formula R1 and R2 independently of one another are hydrogen unsubstituted or substituted C1-12 alkyl unsubstituted or substituted C3-C12 cycloalkyl unsubstituted or substituted C6- C20 aryl or unsubstituted or substituted C2-C20 alkenyl R3 is PO3R1R2 COOR6 COR7 CONR7R8 -SO2R6 CN unsubstituted or substituted C6- C20 aryl R4 is unsubstituted C6-C20 aryl or C6-C20 aryl which is substituted by at least one C1-C18 alkyl, C1-C18 alkoxy, C3-C12 cycloalkyl, hydroxy, amino, mono- ordi-C1-C18 alkylamino, -NR10COR11 or the radical of formula (1a)or unsubstituted or substituted C4-C20 heteroaryl R5 is hydrogen substituted or unsubstituted C1-C20 alkyl unsubstituted or substituted C3- C12 cycloalkyl unsubstituted or substituted C6-C20 aryl or unsubstituted or substituted C4- C20 heteroaryl or R4 and R5 form a cycloaliphatic ring R6, R7 and R8 independently from each other are hydrogen C1-C18 alkyl or C3-C12 cycloalkyl, which may be substituted by one or more E and/or interrupted by one or more D or C6- C20 aryl, which may be substituted by G or R7 and R8 together form a five or six membered ring D is -CO- -COO- -S- -SO- -SO2- -O- -NR9- -SiR12R13- -POR14- -CR15=CR16- or -C≡C- E is -OR17 -SR17 -NR10Rn -NR10COR11 -COR11 -COOR11 -CONR10R11 -CN halogen SO3R18 SO2R18 PO3(R18)2 or PO2(R18)2 G is E C1-C18 alkyl, which is optionally interrupted by D C1-C18 perfluoroalkyI C1-C18 alkoxy, which is optionally substituted by E and/or interrupted by D wherein R9, R10 and R11, independently of each other are hydrogen C6-C18 aryl which is optionally substituted by C1-C18 alkyl or C1-C18 alkoxy C1-C18 alkyl, which is optionally interrupted by -0- or R10 and R11 together form a five or six membered ring R12 and R13 independently of each other are hydrogen C1-C18 alkyl or C6-C18 aryl which is optionally substituted by C1-C18 alkyl R14 is C1-C18 alkyl or C6-C18 aryl, which is optionally substituted by C1-C18 alkyl R15 and R16 independently of each oth
