Liquid electrophotographic ink composition

1. A method of producing a white liquid electrophotographic ink composition, the method comprising:

heating a polymer resin in a carrier fluid to dissolve the polymer resin;

suspending in the carrier fluid white pigment particles to be coated; and

cooling the carrier fluid at a rate of 2° C./hr or less to effect precipitation of the polymer resin from the carrier fluid such that a coating of the resin is formed on the pigment particles, thereby producing the white liquid electrophotographic ink composition.

2. The method according to claim 1 , wherein the carrier fluid is or comprises an isoparaffinic carrier fluid.

3. The method according to claim 1 , wherein the carrier fluid is heated to at least 100° C. to dissolve the polymer resin.

4. The method according to claim 1 , wherein the white pigment particle is or comprises titanium dioxide.

5. The method according to claim 1 , wherein the polymer resin comprises a polymer having acidic side groups.

6. The method according to claim 1 , wherein the polymer resin comprises a copolymer of an alkylene monomer and a monomer selected from the group consisting of acrylic acid and methacrylic acid.

7. The method according to claim 6 , wherein the alkylene monomer is selected from the group consisting of ethylene and propylene.

8. The method according to claim 1 , further comprising grinding the polymer resin coated white pigment particles.

9. The method according to claim 1 , further comprising adding a charge director:

to the carrier liquid before precipitation of the polymer resin; or

to the carrier liquid during precipitation of the polymer resin; or

to the carrier liquid after precipitation of the polymer resin.

10. A liquid electrophotographic ink composition comprising coated pigment particles and having a particle conductivity of less than 100 pmho/cm producible in accordance with a method comprising:

heating a polymer resin in a carrier fluid to dissolve the polymer resin;

suspending in the carrier fluid white pigment particles to be coated; and

cooling the carrier fluid at a rate of 2° C./hr or less to effect precipitation of the polymer resin from the carrier fluid such that a coating of the resin is formed on the pigment particles, thereby producing the white liquid electrophotographic ink composition.

11. A white liquid electrophotographic ink composition, the composition comprising:

a carrier fluid; and

white pigment particles having a polymer resin coating thereon, wherein the polymer resin comprises a copolymer of an alkylene monomer and acrylic acid; and wherein the white liquid electrophotographic ink composition has a particle conductivity of less than 100 pmho/cm.

12. The white liquid electrophotographic ink composition according to claim 11 , wherein the white pigment particle is or comprises titanium dioxide.

13. The white liquid electrophotographic ink composition according to claim 11 , wherein the white pigment particle comprises surface modifying groups to increase hydrophobicity.

14. The white liquid electrophotographic ink composition according to claim 11 , wherein the polymer resin comprises blend of i) the copolymer of the alkylene monomer and acrylic acid, wherein the alkylene monomer is ethylene, and ii) a copolymer of ethylene and methacrylic acid.

15. The white liquid electrophotographic ink composition according to claim 11 , wherein the carrier fluid is or comprises an isoparaffinic carrier fluid.

16. The white liquid electrophotographic ink composition according to claim 11 , further comprising a charge director.

17. The white liquid electrophotographic ink composition according to claim 11 , wherein the alkylene monomer is selected from the group consisting of ethylene and propylene.