Inkjet receiving media

1. An inkjet receiving medium comprising a substrate and a topcoat layer disposed thereon, which topcoat layer comprises:

(a) one or more water-soluble salts of a multivalent metal cation; and

(b) composite particles having a Rockwell Hardness of less than or equal to R90 and each of the composite particles comprising domains of a (i) first organic polymer and domains of a (ii) second organic polymer, wherein:

the domains of the (ii) second organic polymer are dispersed within the domains of the (i) first organic polymer;

the melting point of the (i) first organic polymer is lower than the melting point of the (ii) second organic polymer; and

the weight ratio of the (i) first organic polymer to the (ii) second organic polymer is chosen such that the (b) composite particles have a density of at least 1.0 g/ml and up to and including 1.5 g/ml.

2. The inkjet receiving medium of claim 1 , wherein the (b) composite particles have a density of at least 1.05 g/ml and up to and including 1.35 g/ml.

3. The inkjet receiving medium of claim 1 , wherein the (b) composite particles have a Rockwell Hardness of less than or equal to R75.

4. The inkjet receiving medium of claim 1 , wherein the (b) composite particles have an average equivalent spherical diameter (ESD) particle size of at least 2 μm and up to and including 12 μm.

5. The inkjet receiving medium of claim 1 , wherein the (b) composite particles comprise domains of a (ii) second organic polymer that comprises poly(tetrafluoroethylene) and domains of a (i) first organic polymer that is a polyethylene, polypropylene, ethylene bi-stearamide, carnauba wax, a synthetic hydrocarbon wax, a polyamide, an ethylene-propylene copolymer, or a combination of two or more of these materials.

6. The inkjet receiving medium of claim 1 , wherein the substrate comprises a hydrophobic surface prior to the topcoat layer being formed thereon, which hydrophobic surface is impermeable to water or an aqueous ink composition, and which topcoat layer provides a hydrophilic surface relative to the hydrophobic surface of the substrate.

7. The inkjet receiving medium of claim 6 , wherein the topcoat layer further comprises a (c) water-soluble or water-dispersible binder material that is a polyvinyl alcohol, polyethylene oxide, polyvinyl amine, a copolymer derived from vinyl alcohol and ethylene oxide, a copolymer derived from vinyl alcohol and a vinyl amine, poly(vinyl pyrrolidone), cellulose or a derivative thereof, gelatin or derivative thereof, a crosslinkable hydrophilic binder polymer, a cationic polyelectrolyte, a polyurethane, or a silanol-modified poly(vinyl alcohol), all of which are different in chemical composition from the (b) composite particles.

8. The inkjet receiving medium of claim 7 , wherein the (c) water-soluble or water-dispersible binder material is present in the topcoat layer at a dry weight of at least 1% and up to and including 69%, based on the total weight of the topcoat layer.

9. The inkjet receiving medium of claim 1 , wherein the topcoat layer further comprises (d) organic or inorganic particles that are different from the (a) one or more water-soluble salts of a multivalent metal cation and from the (b) composite particles.

10. The inkjet receiving medium of claim 9 , wherein the (d) organic or inorganic particles comprise silica.

11. The inkjet receiving medium of claim 1 , wherein the (a) one or more water-soluble salts of a multivalent metal cation comprises a cation that is magnesium (+2), calcium (+2), barium (+2), zinc (+2), or aluminum (+3).

12. The inkjet receiving medium of claim 1 , wherein the (a) one or more water-soluble salts of a multivalent metal cation comprise one or more of CaCl 2 , Ca(CH 3 CO 2 ) 2 , MgCl 2 , Mg(CH 3 CO 2 ) 2 , Ca(NO 3 ) 2 , or Mg(NO 3 ) 2 , or hydrated versions of these salts.

13. The inkjet receiving medium of claim 1 , wherein the topcoat layer has a dry solids coating weight of at least 0.1 g/m 2 and up to and including 10 g/m 2 .

14. The inkjet receiving medium of claim 1 , wherein the (a) one or more water-soluble salts of a multivalent metal cation are present in the topcoat layer in an amount of at least 10 weight % and up to and including 98 weight %.

15. The inkjet receiving medium of claim 1 , wherein the (b) composite particles are present in the topcoat layer in an amount of at least 0.2 weight % and up to and including 30 weight %.

16. The inkjet receiving medium of claim 1 , wherein the substrate is capable of absorbing and transferring an aqueous ink colorant to the substrate interior prior to the topcoat layer being formed thereon.

17. The inkjet receiving medium of claim 1 , wherein the (b) composite particles have a Rockwell Hardness of less than or equal to R75 and are present in the topcoat layer in a dry coating weight of at least 0.01 g/m 2 and up to and including 1 g/m 2 .

18. The inkjet receiving medium of claim 1 , wherein the substrate comprises a water-impermeable support, and a first layer that is disposed on at least one surface of the water-impermeable support and is underneath the topcoat layer.

19. The inkjet receiving medium of claim 18 , wherein the water-impermeable support comprises a polymeric film, or a co-extrudate or a laminate of two or more polymeric films.

20. The inkjet receiving medium of claim 18 , wherein the first layer comprises a polyvinyl alcohol, polyvinyl amine, a copolymer derived from vinyl alcohol and a vinyl amine, a gelatin or gelatin derivative, poly(ethyleneimine), an epoxy resin, a polyurethane, a polyacrylamide or a derivative or copolymer thereof, or mixtures thereof.