Heat transfer printing ink is a new type of ink developed to adapt to the heat transfer printing process. The heat transfer printing process involves printing the pattern onto a plastic film coated with a release layer (mainly PET film) using a gravure printing machine, and then printing hot melt adhesive on the back of the pattern to form a heat transfer printing film. The printed heat transfer film passes through a heat transfer roller with a certain temperature and pressure at the heat transfer factory along with the final substrate before tearing off the film, and the pattern will be transferred onto the final substrate.