Media sheet coatings

Abstract

A coating for a substrate is formed by milling cationic pigment particles in the presence of a water-soluble polymer, where the water-soluble polymer acts as a binder and a dispersant for the cationic pigment particles.

1 . A method of forming a coating for a substrate, comprising:
 milling cationic pigment particles in the presence of a water-soluble polymer, wherein the water-soluble polymer acts as a binder and a dispersant for the cationic pigment particles.   
   
   
       2 . The method of  claim 1 , wherein a bead mill is used to mill the cationic pigment particles in the presence of the water-soluble polymer. 
   
   
       3 . The method of  claim 2 , wherein beads of the bead mill are about 0.1 to about 0.3 of a millimeter in diameter. 
   
   
       4 . The method of  claim 1 , wherein the cationic pigment particles are cationic calcium carbonate particles. 
   
   
       5 . The method of  claim 1 , wherein the water-soluble polymer is selected from the group consisting of a nonionic water-soluble polymer and nonionic polyvinyl alcohol. 
   
   
       6 . The method of  claim 1  further comprises adding the cationic pigment particles to a mill as slurry. 
   
   
       7 . The method of  claim 1  further comprises dispersing the cationic pigment particles in water before milling the cationic pigment particles in the presence of the water-soluble polymer. 
   
   
       8 . The method of  claim 1 , wherein the water-soluble polymer adsorbs onto the cationic pigment particles during milling. 
   
   
       9 . The method of  claim 1 , wherein milling the cationic pigment particles produces cationic particles with a primary particle size corresponding to a mean equivalent spherical diameter of about 10 to about 30 nanometers. 
   
   
       10 . The method of  claim 1 , wherein milling the cationic pigment particles produces aggregate cationic particles with an aggregate particle size corresponding to a mean equivalent spherical diameter of about 60 to about 150 nanometers. 
   
   
       11 . The method of  claim 1  further comprises forming the cationic pigment particles from anionic pigment particles before milling. 
   
   
       12 . The method of  claim 11 , wherein forming the cationic pigment particles from anionic pigment particles comprises using a cationic converter. 
   
   
       13 . The method of  claim 12 , wherein the cationic converter is selected from the group consisting of cationic polymers, amine containing phopshonic acids, and cationic surfactants. 
   
   
       14 . A method of forming a coating for a substrate, comprising:
 adding a slurry of cationic calcium carbonate particles to a bead mill;   adding nonionic polyvinyl alcohol to the bead mill;   milling the cationic calcium carbonate particles in the presence of the nonionic polyvinyl alcohol; and   during milling, adsorbing the nonionic polyvinyl alcohol onto the surfaces of the cationic calcium carbonate particles so as to disperse the cationic calcium carbonate particles in the coating;   wherein the nonionic polyvinyl alcohol further acts as a binder for the cationic pigment particles when the coating is dried.   
   
   
       15 . The method of  claim 14 , wherein the bead mill comprises yttrium stabilized zirconium beads of about 0.1 to about 0.3 of a millimeter in diameter. 
   
   
       16 . The method of  claim 14 , wherein adsorbing the nonionic polyvinyl alcohol onto the surfaces of the cationic calcium carbonate particles acts to reduce the likelihood of flocculation of the cationic calcium carbonate particles. 
   
   
       17 . The method of  claim 14  further comprises adding colorants, optical brighteners, defoamers, wetting agents, or rheology modifiers, or combinations thereof to the mill and milling the colorants, optical brighteners, defoamers, wetting agents or rheology modifiers, or combinations thereof with the calcium carbonate particles and polyvinyl alcohol. 
   
   
       18 . The method of  claim 14  further comprises forming the slurry of cationic calcium carbonate particles from anionic pigment particles before adding the slurry of cationic calcium carbonate particles to the bead mill. 
   
   
       19 . A method of forming a media sheet, comprising:
 forming a liquid coating within a mill, wherein forming the liquid coating comprises:
 milling cationic pigment particles in the presence of a water-soluble polymer; and 
 using the water-soluble polymer to disperse the cationic pigment particles in the liquid coating; 
   applying the liquid coating as received directly from the mill to a substrate;   drying the liquid coating to form an image-receiving layer on the substrate; and   using the water-soluble polymer to bind the cationic pigment particles to each other and to the substrate when the liquid coating is dried.   
   
   
       20 . The method of  claim 19 , wherein the cationic pigment particles are cationic calcium carbonate particles. 
   
   
       21 . The method of  claim 19 , wherein the water-soluble polymer is selected from the group consisting of a nonionic water-soluble polymer and nonionic polyvinyl alcohol. 
   
   
       22 . The method of  claim 19 , wherein milling the cationic pigment particles produces cationic particles with a primary particle size corresponding to a mean equivalent spherical diameter of about 10 to about 30 nanometers. 
   
   
       23 . The method of  claim 19 , wherein each gram of the image-receiving layer can absorb about 0.34 to about 0.63 of gram of water. 
   
   
       24 . A media sheet, comprising:
 a substrate; and   an image-receiving layer formed on the substrate;   wherein the image-receiving layer comprises cationic calcium carbonate particles disposed in a nonionic binder, the calcium carbonate particles having a primary particle size corresponding to a mean equivalent spherical diameter of about 10 to about 30 nanometers; and   wherein each gram of the image-receiving layer can absorb about 0.34 to about 0.63 of gram of water.   
   
   
       25 . The media sheet of  claim 24 , wherein the binder is selected from the group consisting of water-soluble binders and polyvinyl alcohol. 
   
   
       26 . The media sheet of  claim 24 , wherein the image-receiving layer has a 60-degree gloss level of about 20 to about 30.