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;

cooling the carrier fluid to effect precipitation of the polymer resin from the carrier fluid such that a coating of the resin is at least partially formed on the pigment particles;

reheating the suspension of partially coated white pigment particles in the carrier fluid; and

cooling the carrier fluid at a controlled rate 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. A method according to claim 1 , wherein the carrier fluid is or comprises an isoparaffinic carrier fluid.

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

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

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

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

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

8. A method according to claim 1 , further comprising adding a charge director.

9. A liquid electrophotographic ink composition comprising coated pigment particles 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;

cooling the carrier fluid to effect precipitation of the polymer resin from the carrier fluid such that a coating of the resin is at least partially formed on the pigment particles;

reheating the suspension of partially coated white pigment particles in the carrier fluid; and

cooling the carrier fluid at a controlled rate 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.

10. 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 methacrylic acid;

and wherein the white liquid electrophotographic ink composition has a particle conductivity of less than 200 phmo/cm.

11. A white liquid electrophotographic ink composition according to claim 10 , wherein the white pigment particle is or comprises titanium dioxide.

12. A white liquid electrophotographic ink composition according to claim 10 , wherein the white pigment particle comprises surface modifying groups to increase hydrophobicity.

13. A white liquid electrophotographic ink composition according to claim 10 , wherein the polymer resin comprises blend of a copolymer of an alkylene monomer and acrylic acid and a copolymer of an alkylene monomer and methacrylic acid.

14. A white liquid electrophotographic ink composition according to claim 10 , wherein the carrier fluid is or comprises an isoparaffinic carrier fluid.

15. A white liquid electrophotographic ink composition according to claim 10 , further comprising a charge director.