Non-aqueous pigment dispersions using dispersion synergists

1. A non-aqueous pigment dispersion comprising:

a diketopyrrolo-pyrrole pigment, a polymeric dispersant, and a dispersion synergist in a dispersion medium; wherein

the dispersion synergist is a quinacridone derivative containing at least one acid group or a salt thereof; and

the quinacridone derivative is substituted on only one of two nitrogen atoms of the quinacridone basic chromophore structure by at least one acid group or a salt thereof.

2. The non-aqueous pigment dispersion according to claim 1 , wherein the at least one acid group or a salt thereof is selected from the group consisting of an alkanoic acid group, an alicyclic acid group, a heterocyclic acid group, a hetero-aromatic acid group, an aromatic acid group, or salts thereof.

3. The non-aqueous pigment dispersion according to claim 2 , wherein the aromatic acid group or a salt thereof is a benzoic acid group, a phthalic acid group, an isophthalic acid group, a terephthalic acid group, or salts thereof.

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

5. The non-aqueous pigment dispersion according to claim 4 , 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 .

6. The non-aqueous pigment dispersion according to claim 1 , wherein the at least one acid group or a salt thereof is a group comprising a carboxyl group or a salt thereof.

7. The non-aqueous pigment dispersion according to claim 1 , wherein the quinacridone derivative is represented by Formula (I):

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

8. The non-aqueous pigment dispersion according to claim 7 , wherein the diketopyrrolo-pyrrole pigment is selected from the group consisting of C.I. Pigment Orange 71, C.I. Pigment Orange 73, C.I. Pigment Orange 81, C.I. Pigment Red 254, C.I. Pigment Red 255, C.I. Pigment Red 264, C.I. Pigment Red 270, C.I. Pigment Red 272, and mixed crystals thereof.

9. 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.