Inkjet printing of color filters

Abstract

A method for printing includes providing a substrate on which a matrix of color elements is defined, the color elements having respective center lines. A printhead assembly is positioned over the substrate. The printhead assembly includes multiple controllable nozzles. At least one of the substrate and the printhead assembly is translated so that the printhead assembly scans over the substrate in a scan direction transverse to the center lines of the color elements. Droplets of ink are ejected from the nozzles onto the substrate at selected times while the printhead assembly scans over the substrate. The times at which to eject the droplets are selected so as to cause the droplets to land on the color elements at respective locations, such that respective locations are displaced from the center lines.

1 . A method for printing, comprising: 
 providing a substrate on which a matrix of color elements is defined, the color elements having respective center lines;    positioning a printhead assembly over the substrate, the printhead assembly comprising multiple controllable nozzles;    translating at least one of the substrate and the printhead assembly so that the printhead assembly scans over the substrate in a scan direction transverse to the center lines of the color elements;    ejecting droplets of ink from the nozzles onto the substrate at selected times while the printhead assembly scans over the substrate; and    selecting the times at which to eject the droplets so that the droplets are aimed to land on the color elements at respective locations, to a side of the center lines.    
     
     
         2 . The method according to  claim 1 , wherein providing the substrate comprises creating elevated borders on the substrate surrounding and defining the color elements.  
     
     
         3 . The method according to  claim 2 , wherein ejecting the droplets comprises directing at least some droplets to contact the borders.  
     
     
         4 . The method according to  claim 1 , wherein the color elements are arranged in rows along a direction transverse to the scan direction, and wherein ejecting the droplets comprises coloring successive, neighboring rows with different, respective colors in alternation.  
     
     
         5 . The method according to  claim 1 , wherein ejecting the droplets comprises actuating the nozzles so as to deposit two or more of the droplets on each of the color elements during a single pass of the printhead over the color elements.  
     
     
         6 . The method according to  claim 5 , wherein actuating the nozzles comprises depositing the two or more of the droplets side by side along an axis transverse to the scan direction.  
     
     
         7 . The method according to  claim 5 , wherein actuating the nozzles comprises depositing the two or more of the droplets in succession along the scan direction.  
     
     
         8 . The method according to  claim 5 , wherein actuating the nozzles comprises depositing the two or more of the droplets so that the two or more of the droplets overlap and coalesce within each of the color elements on the substrate.  
     
     
         9 . The method according to  claim 5 , wherein the printhead assembly comprises multiple, staggered printheads, each comprising a respective plurality of the nozzles, and wherein actuating the nozzles comprises ejecting the two or more of the droplets from different ones of the printheads.  
     
     
         10 . The method according to  claim 1 , wherein selecting the times comprises displacing the droplets from the center lines so as to compensate for motion of the printhead assembly relative to the substrate.  
     
     
         11 . The method according to  claim 1 , wherein the substrate comprises a glass, and wherein ejecting the droplets comprises coloring the color elements so as to serve as a filter overlay for a flat panel display.  
     
     
         12 . The method according to  claim 1 , wherein the substrate comprises a glass, and wherein ejecting the droplets comprises ejecting a polymer operative to selectively emit a colored light so as to serve as an OLED element.  
     
     
         13 . The method according to  claim 1 , wherein the printhead assembly comprises multiple printing units, each comprising a respective plurality of the nozzles, wherein the printing units are distributed along the printhead assembly, and comprising associating a respective cleaning unit with each of the printing units and, after scanning the printhead assembly over the substrate, cleaning excess ink off each of the printing units using the respective cleaning unit.  
     
     
         14 . A method for printing, comprising: 
 providing a substrate on which a matrix of color elements is defined;    positioning a printhead assembly over the substrate, the printhead assembly comprising multiple controllable nozzles;    translating at least one of the substrate and the printhead assembly so that the printhead assembly scans over the substrate in a scan direction;    ejecting droplets of ink from the nozzles onto the substrate at selected times while the printhead assembly scans over the substrate so as to deposit two or more of the droplets on each of the color elements during a single pass of the printhead over the color elements; and    selecting the times at which to eject the droplets so as to cause the droplets to land on the color elements so that the two or more of the droplets overlap and coalesce within each of the color elements on the substrate.    
     
     
         15 . The method according to  claim 14 , wherein ejecting the droplets comprises depositing the two or more of the droplets side by side along an axis transverse to the scan direction.  
     
     
         16 . The method according to  claim 14 , wherein ejecting the droplets comprises depositing the two or more of the droplets in succession along the scan direction.  
     
     
         17 . The method according to  claim 14 , wherein the printhead assembly comprises one or more printing units, each printing unit comprising multiple, staggered printheads for ejecting the droplets of ink of a given color, each printhead comprising a respective plurality of the nozzles, and wherein actuating the nozzles comprises ejecting the two or more of the droplets from different ones of the printheads.  
     
     
         18 . The method according to  claim 17 , wherein the nozzles in each of the multiple, staggered printheads in each printing unit are displaced by respective offsets in a direction transverse to the scan direction, wherein the respective offsets do not increase monotonically across the printing unit.  
     
     
         19 . Apparatus for printing on a substrate on which a matrix of color elements is defined, the color elements having respective center lines, the apparatus comprising: 
 a printhead assembly, which is arranged to be positioned over the substrate, the printhead assembly comprising multiple controllable nozzles;    a translation assembly, which is arranged to translate at least one of the substrate and the printhead assembly so that the printhead assembly scans over the substrate in a scan direction transverse to the center lines of the color elements; and    a controller, which is coupled to drive the printhead assembly to eject droplets of ink from the nozzles onto the substrate at selected times while the printhead assembly scans over the substrate, while selecting the times at which to eject the droplets so as to cause the droplets to land on the color elements at respective locations, such that respective locations are displaced from the center lines.    
     
     
         20 . The apparatus according to  claim 19 , wherein the substrate comprises elevated borders, surrounding and defining the color elements, and wherein the controller is operative to drive the printhead assembly so that the ejected droplets contact the borders.  
     
     
         21 . The apparatus according to  claim 19 , wherein the color elements are arranged in rows along a direction transverse to the scan direction, and wherein the controller is operative to drive the printhead assembly so as to color successive, neighboring rows with different, respective colors in alternation.  
     
     
         22 . The apparatus according to  claim 19 , wherein the controller is operative to drive the printhead assembly so that the nozzles deposit two or more of the droplets on each of the color elements during a single pass of the printhead over the color elements.  
     
     
         23 . The apparatus according to  claim 22 , wherein the two or more of the droplets are deposited side by side along an axis transverse to the scan direction.  
     
     
         24 . The apparatus according to  claim 22 , wherein the two or more of the droplets are deposited in succession along the scan direction.  
     
     
         25 . The apparatus according to  claim 24 , wherein the two or more of the droplets are deposited so as to overlap and coalesce within each of the color elements on the substrate.  
     
     
         26 . The apparatus according to  claim 24 , wherein the printhead assembly comprises multiple, staggered printheads, each comprising a respective plurality of the nozzles, and wherein the two or more of the droplets are ejected from different ones of the printheads.  
     
     
         27 . The apparatus according to  claim 19 , wherein the controller is adapted to select the times so as to compensate for motion of the printhead assembly relative to the substrate.  
     
     
         28 . The apparatus according to  claim 19 , wherein the substrate comprises a glass, and wherein the ink is adapted to color the color elements so as to serve as a filter overlay for a flat panel display.  
     
     
         29 . The apparatus according to  claim 19 , wherein the substrate comprises a glass, and wherein the ink comprises a polymer operative to emit colored light in response to an electrical signal.  
     
     
         30 . The apparatus according to  claim 19 , wherein the printhead assembly comprises multiple printing units, each comprising a respective plurality of the nozzles, wherein the printing units are distributed along the printhead assembly, and comprising multiple cleaning units, which are associated respectively with the multiple printing units and which are operative, after the printhead assembly has scanned over the substrate, to clean excess ink off the respective printing units.  
     
     
         31 . Apparatus for printing on a substrate on which a matrix of color elements is defined, the apparatus comprising: 
 a printhead assembly, which is arranged to be positioned over the substrate, the printhead assembly comprising multiple controllable nozzles;    a translation assembly, which is arranged to translate at least one of the substrate and the printhead assembly so that the printhead assembly scans over the substrate in a scan direction; and    a controller, which is coupled to drive the printhead assembly to eject droplets of ink from the nozzles onto the substrate at selected times while the printhead assembly scans over the substrate so as to deposit two or more of the droplets on each of the color elements during a single pass of the printhead over the color elements, while selecting the times at which to eject the droplets so as to cause the droplets to land on the color elements so that the two or more of the droplets overlap and coalesce within each of the color elements on the substrate.    
     
     
         32 . The apparatus according to  claim 31 , wherein the two or more of the droplets are deposited side by side along an axis transverse to the scan direction.  
     
     
         33 . The apparatus according to  claim 31 , wherein the two or more of the droplets are deposited in succession along the scan direction.  
     
     
         34 . The apparatus according to  claim 31 , wherein the printhead assembly comprises one or more printing units, each printing unit comprising multiple, staggered printheads for ejecting the droplets of ink of a given color, each printhead comprising a respective plurality of the nozzles, and wherein the two or more of the droplets are ejected from different ones of the printheads.  
     
     
         35 . The apparatus according to  claim 34 , wherein the nozzles in each of the multiple, staggered printheads in each printing unit are displaced by respective offsets in a direction transverse to the scan direction, wherein the respective offsets do not increase monotonically across the printing unit.