Non-aqueous pigment dispersions using dispersion synergists

1. A non-aqueous pigment dispersion comprising:

a quinacridone pigment, a polymeric dispersant, and a dispersion synergist in a dispersion medium; wherein

the dispersion synergist is a diketopyrrolo-pyrrole derivative containing at least one acidic group or a salt thereof;

the dispersion synergist is a diketopyrrolo-pyrrole derivative according to Formula (I):

wherein R 1 , R 2 , and R 3 are inderendently selected from the group consisting of hydrogen, a halogen atom, a methyl group, an ethyl group, a tert.-butyl group, a phenyl group, a cyano group, and an acidic group;

R 4 and R 6 are independently selected from the group consisting of hydrogen and a halogen atom;

R 5 is independently selected from the grourp consisting of hydrogen, a halogen atom, a methyl group, an ethyl group, a tert.-butyl group, and a cyano group; and

one of R 7 and R 8 is a group including at least one acidic group while the other one of R 7 and R 8 represents hydrogen.

2. The non-aqueous pigment dispersion according to claim 1 , wherein the acidic group for R 1 , R 2 , and/or R 3 is a carboxyl group.

3. The non-aqueous pigment dispersion according to claim 1 , wherein R 1 and R 3 represent a carboxyl group and R 2 represents hydrogen.

4. The non-aqueous pigment dispersion according to claim 1 , wherein R 1 , R 2 , and R 3 are independently selected from the group consisting of hydrogen, a halogen atom, a methyl group, an ethyl group, a tert.-butyl group, a phenyl group, and a cyano group.

5. The non-aqueous pigment dispersion according to claim 3 , wherein R 1 , R 3 , R 4 , and R 6 represent hydrogen.

6. The non-aqueous pigment dispersion according to claim 5 , wherein R 2 and R 5 represent a chloro atom.

7. The non-aqueous pigment dispersion according to claim 5 , wherein R 2 and R 5 represent hydrogen.

8. The non-aqueous pigment dispersion according to claim 1 , wherein one of R 7 and R 8 is a group including two acidic groups while the other one of R 7 and R 8 represents hydrogen.

9. The non-aqueous pigment dispersion according to claim 1 , wherein the group including two acid functions R 7 or R 8 is selected from the group consisting of an alkanoic acid group, an alicyclic acid group, a heterocyclic acid group, a heteroaromatic acid group, and an aromatic acid group.

10. The non-aqueous pigment dispersion according to claim 9 , wherein the aromatic acid group is a phthalic acid group, an isophthalic acid group, or a terephthalic acid group.

11. The non-aqueous pigment dispersion according to claim 1 , wherein the salt of the group including the at least one acidic group is an ammonium acid salt group.

12. The non-aqueous pigment dispersion according to claim 11 , wherein the ammonium acid salt group is a substituted ammonium group selected from the group consisting of + N(CH 3 ) 2 (C 18 H 37 ) 2 , + NH(CH 3 ) 2 (C 18 H 37 ), + N(CH 3 ) 2 (C 12 H 25 ) 2, + NH(CH 3 ) 2 (C 12 H 25 ), + N(CH 3 ) 2 (C 10 H 21 ) 2 , + NH(CH 3 ) 2 (C 10 H 21 ), + N(CH 3 ) 2 (C 8 H 17 ) 2, + NH(CH 3 ) 2 (C 8 H 17 ), + NH(C 8 H 17 ) 3 , + NH(C 10 H 21 ) 3 , + NH(C 12 H 25 ) 3 , and + NH(C 18 H 35 ) 3 .

13. The non-aqueous pigment dispersion according to claim 1 , wherein the non-aqueous pigment dispersion is a curable inkjet ink or a non-aqueous inkjet ink containing an organic solvent and/or oil.