Method and apparatus for controlling lightness in colored inkjet inks by means of a transparent white ink composition

Abstract

A transparent white ink composition is formulated to brighten, lighten and or dilute full-tone primary inkjet colors: cyan; magenta; yellow and black, eliminating the need for ‘light ink’ primary color inks. The transparent white ink is jetted concurrently with reduced amounts of full-tone inks in lighter tonal areas conventionally supported by ‘light ink’ primary inks. Printing ‘light ink’ primary colors using a transparent white ink composition may reduce the number of print channels needed to print all four primary colors and the four ‘light ink’ primary colors. Embodiments of the transparent white ink composition may be solvent- or water-based, drying by evaporation of the carrier fluid. Other embodiments may be radiation-curable ink compositions. An inkjet printer includes print carriage and print head assemblies configured for jetting a primary color ink and the transparent white ink in the same pass in correct proportions to achieve a desired effect.

1 . A transparent white inkjet ink comprising one or more of:
 a dendritic or hyperbranched polyester acrylate component present in said composition in an amount of 10% to 45% by weight of said composition;   an oligomer component present in said composition in an amount of 1% to 15% by weight of said composition;   a monomer component present in said composition in an amount of 30% to 60% by weight of said composition;   a photo-initiator component present in said composition in an amount of 1% to 20% by weight of said composition; and   a colorant component present in said composition in an amount of no greater than 5% by weight of said composition, said colorant comprising at least one white pigment.   
     
     
         2 . The ink composition of  claim 1 , wherein said at least one pigment comprises at least one compound selected from a group including: titanium dioxide and zinc oxide. 
     
     
         3 . The ink composition of  claim 1 , further comprising an additive component, said additive component including at least one selected from a group comprising:
 at least one surfactant present in said composition in an amount of 0.01% to 2% by weight of said composition;   at least one leveling additive present in said composition in an amount of 0.01% to 2% by weight of said composition; and   at least one stabilizer present in said composition in an amount of 0.01% to 2% by weight of said composition.   
     
     
         4 . The ink composition of  claim 1 , further comprising a co-initiator component present in said composition in an amount no greater than 15% by weight of said composition. 
     
     
         5 . A method for producing a lightened primary color inkjet ink comprising:
 blending a primary color inkjet ink and a transparent white inkjet ink by jetting both inks onto a predetermined area of a substrate so that the two inks blend with each other in the predetermined area of the substrate, wherein sad blended inks comprise a lightened primary color inkjet ink; and   curing said blended inks.   
     
     
         6 . A system for producing a composite lightened primary color inkjet ink comprising:
 a plurality of inkjet inks, each of a different primary color;   a transparent white ink as in any of  claims 1 - 4 ;   an inkjet printer having a plurality of color channels;   a controller for said inkjet printer; and   program code for controlling said inkjet printer, which when executed by said controller causes said inkjet printer to perform computer-implemented operations including:
 allocating one of said plurality of color channels for delivery of said transparent white ink to a substrate; 
 responsive to instructions from a page description to deliver a pre-formulated light inkjet ink of a predetermined primary color to a predetermined region of said substrate:
 jetting an amount of a first inkjet ink onto said predetermined region; 
 while said first inkjet ink remains uncured, jetting an amount of a second inkjet ink onto said predetermined region of said substrate; 
 wherein said first ink is selected from a group comprising the primary color inkjet ink specified by said page description and the transparent white inkjet ink and wherein said second inkjet ink comprises the remaining inkjet ink in said group after selection of said first inkjet ink; and 
 curing said amounts of said first and second inkjet inks jetted onto said predetermined region; 
 wherein blending of said first and second inkjet inks on said predetermined region in their uncured state produces a lightened primary color inkjet ink that replaces said pre-formulated light inkjet ink specified by said page description. 
 
   
     
     
         7 . The system of  claim 6 , wherein said first inkjet ink comprises said primary color inkjet ink and wherein said second inkjet ink comprises said transparent white inkjet ink. 
     
     
         8 . The system of  claim 6 , wherein said first inkjet ink comprises said transparent white inkjet ink and said second inkjet ink comprises said primary color inkjet ink. 
     
     
         9 . The system of  claim 6 , wherein said primary color inkjet ink is selected from a group consisting of cyan, magenta, yellow and black inkjet inks. 
     
     
         10 . The system of  claim 6 , wherein said amount of said transparent white inkjet ink is selected to lighten said amount of primary color inkjet ink to a lightness equal to that of said pre-formulated light inkjet ink specified by said page description. 
     
     
         11 . The system of  claim 6 , the computer-implemented operations further comprising:
 jetting said first and second inkjet inks from separate color channels.   
     
     
         12 . A method for producing a composite inkjet ink comprising:
 jetting at least one liquid inkjet ink onto a predetermined region of a substrate;   while said at least one liquid inkjet ink remains uncured, jetting an amount of at least one second liquid onto said predetermined region of said substrate;   wherein said at least one second liquid is selected from a group comprising at least one further inkjet ink different from said at least one liquid inkjet ink and at least one non-ink liquid;   wherein said at least one liquid inkjet ink jetted onto said predetermined region of said substrate and said at least one second liquid jetted onto said predetermined region of said substrate blend to form a single composite inkjet ink.