COLORLESS SALT OF HETEROPOLY ACID AS CHARGE CONTROL SUBSTANCE IN TONER

Heteropolyacid salts of the formula I R1 and R2 independently of one another stand for hydrogen, chlorine, bromine, hydroxyl, C1- to C4-alkoxy, nitro or carboxyl, A stand for C1- to C5-alkylene or -C6H4-CH2- (m- or p-), m stands for 0 or 1, n stands for 1 or 2, K(+) stands for R3 stands for C1- to C24-alkyl, carbamoyl-C1- to C2-alkyl, C1- to C4-alkoxycarbonyl-C1- to C2-alkyl, benzyl, cyclohexyl or allyl, R4 stands for C1- to C4-alkyl or a single bond linked to D, R5 stands for C1- to C4-alkyl, D stands for -CH2-, -CH2-CO-, -CH2-CO-NH- or -CH2-CO-NH-CH2-, W stands for CO or for single bond, Z stands for -CH2-, -O-, -S-, -SO2- or a single bond and X(-) stands for an anion of a heteropolyacid based on tungsten and/or molybdenum containing phosphorus, silicon, vanadium, cobalt, nickel, manganese, chromium and/or aluminum, are used as additives for reinforcing the positive charge in electrographic toners.