Diketopyrrolopyrrole pigments

1. A diketopyrrolopyrrole of the formula (I)

wherein

R 1 , R 2 , R 3 and R 4 independently of one another are a C 1 –C 4 alkyl radical or a substituted or unsubstituted phenyl radical, wherein the substituted phenyl radical is substituted by 1, 2, 3 or 4 substituents selected from the group consisting of C 1 –C 4 alkyl, C 1 –C 4 alkoxy, CN, F, Cl, Br, NO 2 , CF 3 , S—C 1 –C 4 alkyl, phenyl and (C 1 –C 2 )alkylenephenyl,

with the proviso that at least one of the radicals, R 1 , R 2 , R 3 , or R 4 , is a substituted or unsubstituted phenyl radical.

2. A diketopyrrolopyrrole as claimed in claim 1 , wherein the radicals R 1 and R 4 are identical and the radicals R 2 and R 3 are identical.

3. A diketopyrrolopyrrole as claimed in claim 1 , wherein the radicals R 1 , R 2 , R 3 and R 4 independently of one another are methyl, ethyl, phenyl or phenyl substituted by 1 or 2 substituents selected from the group consisting of methyl, ethyl, methoxy, ethoxy, CN, F, Cl, S-methyl, phenyl and benzyl.

4. A diketopyrrolopyrrole as claimed in claim 1 , wherein R 1 and R 4 are each a methyl or ethyl group and R 2 and R 3 are each an identical phenyl radical which is unsubstituted or substituted by 1 or 2 substituents selected from the group consisting of methyl, ethyl, methoxy, ethoxy, F, Cl, NO 2 , CF 3 , phenyl and benzyl.

5. A mixture of two or more diketopyrrolopyrroles as claimed in claim 1 .

6. A process for preparing a diketopyrrolopyrrole as claimed in claim 1 , comprising the steps of reacting a succinic diester with a nitrile of the formula (II) (III), or with a mixture of 2, 3 or 4 different nitriles of the formula (II) or (III),

in an organic solvent in the presence of a strong base and subsequently hydrolyzing.

7. A process for preparing a diketopyrrolopyrrole of the formula (I) as claimed in claim 1 , comprising the steps of reacting an ester of the formulae (IV) or (V)

in which R 5 and R 6 are an unsubstituted or substituted alkyl or aryl radical, with a nitrile of the formula (III)

in an organic solvent in the presence of a strong base and subsequently hydrolyzing.

8. A pigmented high molecular mass organic material of natural or synthetic origin pigmented with at least one diketopyrrolopyrrole as claimed in claim 1 .

9. The pigmented high molecular mass organic material as claimed in claim 8 , wherein the pigmented high molecular mass material is an ink-jet ink.

10. A compound of the formula (IV)

wherein R 5 and R 6 are an unsubstituted or substituted alkyl or aryl radical and R 1 and R 2 independently of one another are a C 1 –C 4 alkyl radical or a substituted or substituted phenyl radical, wherein the unsubstituted phenyl radical is substituted by 1, 2, 3 or 4 substituents selected from the group consisting of C 1 –C 4 alkyl, C 1 –C 4 alkoxy, CN, F, Cl, Br, NO 2 , CF 3 , S—C 1 –C 4 alkyl, phenyl and (C 1 –C 2 )alkylenephenyl, with the proviso that at least one of the radicals, R 1 and R 2 is a substituted or unsubstituted phenyl radical.

11. The pigmented high molecular mass organic material as claimed in claim 8 , wherein the pigmented high molecular mass material is selected from the group consisting of plastics, resins, varnishes, paints, electrophotographic toners, electrophotographic developers, color filters, drawing inks, writing inks and printing inks.

12. A compound of the formula (V)

wherein R 5 is an unsubstituted or substituted alkyl or aryl radical and R 1 and R 2 independently of one another are a C 1 –C 4 alkyl radical or a substituted or substituted phenyl radical, wherein the unsubstituted phenyl radical is substituted by 1, 2, 3 or 4 substituents selected from the group consisting of C 1 –C 4 alkyl, C 1 –C 4 alkoxy, CN, F, Cl, Br, NO 2 , CF 3 , S—C 1 –C 4 alkyl, phenyl and (C 1 –C 2 )alkylenephenyl, with the proviso that at least one of the radicals, R 1 and R 2 is a substituted or unsubstituted phenyl radical.