Patent ID: 8658704

Claim:
A composite printing medium for digital printing, comprising: a substrate having a surface; and a coating layer, wherein the coating layer is formed by evenly coating a coating slurry on the surface of the substrate and drying, and the coating slurry comprises: χ-alumina dispersion, wherein the χ-alumina dispersion comprises flaked porous χ-alumina nanoparticles evenly dispersing in water or acidic solution without gamma (γ)-alumina, and the flaked porous χ-alumina nanoparticles are formed by subjecting gibbsite to thermal treating, physical wet-milling and pH adjusting processes, and the flaked porous χ-alumina nanoparticles have a specific surface area of 100 m 2 /g to 220 m 2 /g, an average thickness of 10 nm to 200 nm, an average cross-sectional diameter of 20 nm to 1000 nm and pore size over a surface of the flaked porous χ-alumina nanoparticles of 1 nm to 10 nm; and an adhesive added into the coating slurry in an amount of 8 wt. % to 20 wt. %, wherein the adhesive is selected from the group consisted of poly(vinyl alcohol) (PVA), casein, rosin glue and paraffin glue; wherein the coating slurry without dyes and pigments has a solid content of 20 wt. % to 40 wt. %, a pH value of 2 to 6, and the coating layer formed by the coating slurry has water resistance and an ink absorptivity of 1.5 mg/cm 2 to 1.8 mg/cm 2 .