Non-aqueous pigmented inkjet inks

1. A non-aqueous inkjet ink comprising:

a benzimidazolone pigment; and

a polymeric dispersant according to Formula (I):

wherein

T represents hydrogen or a polymerization terminating group;

Z represents the residue of hyperbranched polyethyleneimine having a number-average molecular weight of at least 100;

A represents one or more oxyalkylene carbonyl groups selected from the group consisting of oxyalkylene carbonyl groups derivable from δ-valerolactone, ε-caprolactone, and C 1-4 -alkyl substituted ε-caprolactone;

T-C(O)A n - represents a TPOAC-chain which is bound to Z through an amide bond; and

n and m are integers wherein m is at least 2 and n is from 2 to 100; and

the polymeric dispersant satisfies the conditions of:

W TPOAC >57 and N Amide ≧65 mol %

wherein

W TPOAC represents a ratio of a weight percentage of the TPOAC-chains over a weight percentage of the amide bonds in the polymeric dispersant;

N Amide represents the mol % of the amide bonds based on a total nitrogen content of the polymeric dispersant; and

the values of W TPOAC and N Amide are calculated from the total nitrogen content determined by dry combustion of the polymeric dispersant and from the amine content determined through potentiometric titration in a mixture of CH 3 COOH:THF (14.5:0.5) with 0.1 N aqueous perchloric acid.

2. The non-aqueous inkjet ink according to claim 1 , wherein the benzimidazolone pigment contains a chromophore according to Formula (II):

wherein

R1 is selected from the group consisting of hydrogen, a halogen atom, a methyl group, an ethyl group, a methoxy group, an ethoxy group, —CF 3 , —COOH, —COOCH 3 ;

and

R2, R4, and R5 are independently selected from the group consisting of hydrogen, a halogen atom, a methyl group, an ethyl group, a methoxy group, an ethoxy group, —CF 3 , —COOH and —COOCH 3 ;

R3 is selected from the group consisting of hydrogen, a halogen atom, a methyl group, an ethyl group, a methoxy group, an ethoxy group, —CF 3 , —COOH, —COOCH 3 , —SO 2 NH—C 6 H 5 , —CONH—C 6 H 5 , —CONH—C 6 H 5 —CONH 2 , and —CONH 2 ; and

R6 and R7 represent the necessary atoms to form an imidazolone ring.

3. The non-aqueous inkjet ink according to claim 2 , wherein the benzimidazolone pigment is C.I. Pigment Yellow 120.

4. The non-aqueous inkjet ink according to claim 2 , wherein the benzimidazolone pigment is selected from the group consisting of C.I. Pigment Yellow 151, 154, 175, 180, 181, and 194.

5. The non-aqueous inkjet ink according to claim 1 , wherein a chain moiety represented by -A n - is a mixture of oxyalkylene carbonyl groups derivable from δ-valerolactone and ε-caprolactone.

6. The non-aqueous inkjet ink according to claim 5 , wherein the mixture contains more than 75 mol % ε-caprolactone.

7. The non-aqueous inkjet ink according to claim 1 , wherein the alkyl substituent of C 1-4 alkyl substituted ε-caprolactone is methyl.

8. The non-aqueous inkjet ink according to claim 1 , wherein T is derived from a mono-carboxylic acid T-COOH selected from the group consisting of an aliphatic acid, an aromatic acid, a hetero-aromatic acid, a heterocyclic acid, and an alicyclic acid.

9. The non-aqueous inkjet ink according to claim 8 , wherein the aliphatic acid is a C 1-25 aliphatic carboxylic acid optionally substituted by hydroxyl, C 1-4 alkyl, or halogen.

10. The non-aqueous inkjet ink according to claim 9 , further comprising a radiation curable compound.

11. A non-aqueous inkjet ink set comprising:

at least one non-aqueous inkjet ink including:

a benzimidazolone pigment; and

a polymeric dispersant according to Formula (I):

wherein

T represents hydrogen or a polymerization terminating group;

Z represents the residue of hyperbranched polyethyleneimine having a number-average molecular weight of at least 100;

A represents one or more oxyalkylene carbonyl groups selected from the group consisting of oxyalkylene carbonyl groups derivable from δ-valerolactone, ε-caprolactone, and C 1-4 -alkyl substituted ε-caprolactone;

T-C(O)A n - represents a TPOAC-chain which is bound to Z through an amide bond; and

n and m are integers wherein m is at least 2 and n is from 2 to 100; and

the polymeric dispersant satisfies the conditions of:

W TPOAC >57 and N Amide ≧65 mol %

wherein

W TPOAC represents a ratio of a weight percentage of the TPOAC-chains over a weight percentage of the amide bonds in the polymeric dispersant;

N Amide represents the mol % of the amide bonds based on a total nitrogen content of the polymeric dispersant; and

the values of W TPOAC and N Amide are calculated from the total nitrogen content determined by dry combustion of the polymeric dispersant and from the amine content determined through potentiometric titration in a mixture of CH 3 COOH:THF (14.5:0.5) with 0.1 N aqueous perchloric acid.

12. The non-aqueous inkjet ink set according to claim 11 , wherein the ink set includes a second non-aqueous inkjet ink comprising C.I. Pigment Violet 19 or a mixed crystal thereof and the polymeric dispersant according to Formula (I).