Electrostatic ink composition
There is provided an electrostatic ink composition comprising chargeable particles comprising white pigment particles having a basic species on their surface; and a charge director; wherein the white pigment particles are present in an amount of at least 75 wt % based on the total weight of the non-volatile solids in the electrostatic ink composition. A method of manufacturing an electrostatic ink composition and a printed medium are also described.
1. An electrostatic ink composition comprising:
a) chargeable particles comprising white pigment particles having a basic species on their surface; and
b) a charge director;
wherein the white pigment particles are present in an amount of at least 75 wt % based on the total weight of the non-volatile solids in the electrostatic ink composition.
2. The electrostatic ink composition according to claim 1 , further comprising a liquid carrier.
3. The electrostatic ink composition according to claim 1 , further comprising a thermoplastic resin.
4. The electrostatic ink composition according to claim 1 , further comprising a dispersant.
5. The electrostatic ink composition according to claim 1 , wherein the basic species on the surface of the white pigment particles is an inorganic species.
6. The electrostatic ink composition according to claim 1 , wherein the white pigment particles comprise a first metal oxide and wherein the species on the surface comprises a second metal oxide.
7. The electrostatic ink composition of claim 1 , wherein the white pigment particles comprise TiO 2 particles and wherein the species on the surface comprises alumina and/or zirconia.
8. The electrostatic ink composition according to claim 5 , wherein the white pigment particles are also surface treated with an organic species selected from silicones and siloxanes.
9. The electrostatic ink composition according to claim 1 , wherein the white pigment is present in an amount of at least 85 wt % based on the total weight of the non-volatile solids in the electrostatic ink composition.
10. The electrostatic ink composition according to claim 1 , wherein the white pigment is present in an amount of at least 90 wt % based on the total weight of the non-volatile solids in the electrostatic ink composition.
11. A method of manufacturing an electrostatic ink composition according to claim 1 , comprising combining
a) chargeable particles comprising white pigment particles having a basic species on their surface; and
b) a charge director;
wherein the white pigment particles are present in an amount of at least 75 wt % based on the total weight of the non-volatile solids in the electrostatic ink composition.
12. The method of claim 11 comprising:
grinding the white pigment particles in a carrier liquid, and wherein a charge director is combined with the white pigment particles before, during or after the grinding to form the electrostatic ink composition.
13. The method of claim 11 comprising:
mixing a resin and a carrier liquid to form a resin paste; and then
grinding the resin paste with the white pigment particles, and wherein a charge director is combined with the pigment and resin paste before, during or after the grinding of the pigment paste with the pigment to form the electrostatic ink composition.
14. A printed medium having printed thereon an electrostatic ink composition comprising:
a) chargeable particles comprising white pigment particles having a basic species on their surface; and
b) a charge director;
wherein the white pigment particles are present in an amount of at least 75 wt % based on the total weight of the non-volatile solids in the electrostatic ink composition.
15. The printed medium according to claim 14 wherein the printed medium comprises a transparent electrostatic ink composition comprising a thermoplastic resin and a charge director and/or charge adjuvant.