Heat transfer printing

1. A process for heat transfer printing, the process comprising:

electrostatically printing a transparent release composition onto a transfer material to form a release layer disposed on the transfer material;

electrostatically printing an electrostatic ink composition to form an image layer disposed on the release layer;

applying a heat-activatable adhesive composition to the image layer to form a heat-activatable adhesive layer;

contacting the heat-activatable adhesive layer with a target substrate under conditions such that the heat-activatable adhesive layer is activated to adhere to the target substrate and the release layer is softened; and

separating the target substrate and the transfer material such that the heat-activatable layer, image layer and release layer are transferred to the target substrate.

2. A process according to claim 1 , wherein the heat-activatable adhesive composition comprises a heat-activatable resin.

3. A process according to claim 2 , wherein the heat-activatable resin is a thermoplastic resin comprising polar sites.

4. A process according to claim 3 , wherein the heat-activatable resin is selected from the group comprising acrylic resins, polyester resins, polyurethane resins, poly vinyl alcohol resins, poly vinyl acetate resins, acrylamide resins, polyamide resins, polyimide resins, epoxy resins, and ionomers.

5. A process according to claim 3 , wherein the heat-activatable resin has a softening temperature in the range of from about 40° C. to about 150° C.

6. A process according to claim 2 , wherein the heat-activatable adhesive composition comprises a water-based emulsion of a heat-activatable resin.

7. A process according to claim 1 , wherein the transparent release composition comprises a thermoplastic resin.

8. A process according to claim 7 , wherein the thermoplastic resin has a softening temperature in the range of about 40° C. to about 150° C.

9. A process according to claim 7 , wherein the transparent release composition further comprises a solid polar compound.

10. A process according to claim 9 , wherein the solid polar compound is present in an amount from about 20 to 60 wt % of the total solids of the transparent release composition.

11. A process according to claim 9 , wherein the solid polar compound is selected from the group consisting of a saccharide, polyacrylic acid, polyvinyl alcohol, styrene maleic anhydride, a bismaleimide oligomer, a cellulose derivative and an aliphatic urethane acrylate.

12. A process according to claim 1 , wherein the target substrate comprises metal or glass.

13. A process according to claim 1 , wherein the heat-activatable adhesive layer and target substrate are contacted at a temperature in the range of about 50° C. to about 250° C.

14. A heat transferable printed image comprising:

a transfer material;

an electrostatically printed transparent release layer disposed on the transfer material;

an electrostatically printed image layer disposed on the release layer; and

a heat-activatable adhesive layer disposed on the image layer.

15. A method of printing a heat transferable image, the method comprising:

electrostatically printing a transparent release composition onto a transfer material to form a release layer disposed on the transfer material;

electrostatically printing an electrostatic ink composition to form an image layer disposed on the release layer;

applying a heat-activatable adhesive composition to the image layer to form a heat-activatable adhesive layer.