Surface modified pigments and non-aqueous inks therewith

1. A method for preparing a surface modified organic pigment, the method comprising the steps of:

reacting an organic pigment in an aromatic hydrocarbon solvent with a surface modifying reagent to form the surface modified organic pigment; and

washing and drying the surface modified organic pigment; wherein

the surface modifying reagent is represented by Formula (I):

X is selected from the group consisting of O, S, and N—R3;

Y is selected from the group consisting of O and NR4;

R1 to R4 are each independently selected from the group consisting of hydrogen, an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an alkaryl group, and an aryl group and a heteroaryl group; and

when Y—R1 is different from OH, at least one of R2 to R4 is substituted by at least one functional group having a pKa between 2.5 and 9.

2. The method according to claim 1 , wherein the surface modifying reagent is represented by Formula (II):

wherein R2 is defined in Formula (I).

3. The method according to claim 1 , wherein X represents O.

4. The method according to claim 1 , wherein R2 is selected from the group consisting of hydrogen, an alkyl group, and an aryl group.

5. The method according to claim 1 , wherein the surface modifying reagent is selected from the group consisting of glyoxylic acid, pyruvic acid, 2-oxobutanoic acid, and phenyl glyoxylic acid.

6. The method according to claim 1 , wherein the organic pigment is selected from the group consisting of quinacridone pigments, diketopyrrolopyrrole pigments, quinolonoquinolone pigments, dioxazine pigments, aminoanthraquinone pigments, indanthrone pigments, bisbenzimidazobenzophenanthroline dione pigments, and mixed crystals thereof.

7. A surface modified organic pigment comprising:

at least one functional group according to Formula (I) attached to its surface:

wherein

the dashed line in Formula I represents a covalent bond to one pigment molecule at a pigment surface;

X is selected from the group consisting of OR5, SR6, NR3R7, and a halogen;

Y is selected from the group consisting of O and NR4;

R1 to R4 are independently selected from the group consisting of hydrogen, an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an alkaryl group, an aryl group, and a heteroaryl group;

R5 to R7 are independently selected from the group consisting of hydrogen, an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an alkaryl group, an aryl group, and a heteroaryl group and an acyl group;

any one of R1 to R7 may represent necessary atoms to form a five to eight membered ring with one of the other groups selected from R1 to R7; and

when Y—R1 is different from OH, at least one of R2 to R7 is substituted by at least one functional group having a pKa between 2.5 and 9.

8. The surface modified organic pigment according to claim 7 , wherein Y represents O, and R1 is hydrogen.

9. The surface modified organic pigment according to claim 7 , wherein X is a hydroxyl group.

10. The surface modified organic pigment according to claim 7 , wherein R2 is selected from the group consisting of hydrogen, an alkyl group, and an aryl group.

11. The surface modified organic pigment according to claim 7 , wherein the one of pigment molecule at the pigment surface is selected from the group consisting of quinacridone, diketopyrrolopyrrole, quinolonoquinolone, dioxazine, aminoanthraquinone, indanthrone, and bisbenzimidazobenzophenanthroline dione.

12. A non-aqueous ink containing a surface modified organic pigment according to claim 7 .

13. The non-aqueous ink according to claim 12 , wherein the non-aqueous ink is a radiation curable ink.

14. The non-aqueous ink according to claim 13 , further comprising a polymerizable compound including at least one vinyl ether group that is a vinyl ether acrylate.

15. The non-aqueous ink claim 12 , wherein the non-aqueous ink is a non-aqueous inkjet ink.