Paper substrate containing a wetting agent and having improved printability

Abstract

The present invention relates to a sizing composition that, when applied to paper substrate, creates a substrate, preferably suitable for inkjet printing, having increased print density, and print mottle, as well as print sharpness, low HST, and/or image dry time, the substrate preferably having high brightness and reduced color-to-color bleed as well. In addition, the present invention relates to a method of reducing the HST of a paper substrate by applying the sizing composition to at least one surface thereof. Further, the application relates to methods of making and using the sizing composition, as well as methods of making and using the paper containing the sizing composition.

What is claimed is: 
     
         1 . A sizing composition, comprising
 at least one binder;   at least one inorganic salt; and   at least one wetting agent.   
     
     
         2 . The sizing composition according to  claim 1 , comprising
 at least two binders;   at least one inorganic salt; and   at least one wetting agent.   
     
     
         3 . The sizing composition according to  claim 1 , wherein the at least two binders are polyvinyl alcohol and starch. 
     
     
         4 . The sizing composition according to  claim 1 , wherein the total binder is present at an amount ranging at least 20 wt %, based upon the total weight of the solids in of the composition. 
     
     
         5 . The sizing composition according to  claim 1 , further comprising an optical brightening agent. 
     
     
         6 . The sizing composition according to  claim 5 , wherein the optical brightening agent is cationic. 
     
     
         7 . The sizing composition according to  claim 6 , wherein the optical brightening agent is a dye fixative. 
     
     
         8 . The sizing composition according to  claim 7 , wherein the optical brightening agent is present at an amount ranging from 1 to 5 wt % based upon the total weight of the solids in of the composition. 
     
     
         9 . The sizing composition according to  claim 1 , comprising
 at least one binder at an amount of at least 20 wt % based upon the total weight of the solids in of the composition;   at least one inorganic salt at an amount ranging from 1 to 25 wt % based upon the total weight of the solids in of the composition, and   at least one wetting agent at an amount ranging from 0.5 to 20 wt % based upon the total weight of the solids.   
     
     
         10 . The sizing composition according to  claim 9 , comprising
 at least two binders wherein the at least two binders are starch and polyvinyl alcohol; and   an optical brightener.   
     
     
         11 . A paper substrate, comprising the sizing composition according to  claim 1 . 
     
     
         12 . The paper substrate according to  claim 11 , wherein the substrate has a print density of at least 0.95. 
     
     
         13 . The paper substrate according to  claim 11 , wherein the substrate has a waterfastness of at least 95%. 
     
     
         14 . The paper substrate according to  claim 11 , wherein the substrate has at least two surfaces, each of said surfaces having a surface print mottle of less than 15.5 as measured by the print non-uniformity index. 
     
     
         15 . The paper substrate according to  claim 11 , wherein the substrate has at least two surfaces, each of said surfaces having a surface print mottle of less than 9.0 as measured by the print non-uniformity index. 
     
     
         16 . The paper substrate according to  claim 15 , wherein the substrate has a print density of at least 1.0 and an HST of not more than 10 seconds. 
     
     
         17 . The paper substrate according to  claim 16 , wherein the substrate has a waterfastness of at least 95%. 
     
     
         18 . A method of making the paper substrate according to  claim 11 , comprising contacting a sizing composition with a web of cellulose fibers, wherein the sizing composition comprises at least one binder, at least one inorganic salt, and at least one wetting agent. 
     
     
         19 . The method according to  claim 18 , wherein the contacting occurs at the wet end, the size press, or the coater. 
     
     
         20 . The method according to  claim 19 , comprising contacting the sizing composition with the web at the size press an amount such that from 50 to 110 lbs of binder is applied per ton of web, from 1.5 to 15 lbs of wetting agent is applied per ton of web, and from 5 to 30 lbs of inorganic salt is applied per ton of web.