Ink Jet UV Curing

Abstract

A method and apparatus for printing a product, article or other object at a printing station and for enhancing the application of UV light to UV photo initiators in a UV curable ink being applied to a product, article or other object at the printing station, comprising the steps for: printing a UV-curable ink with a printing head of a printer on a substrate, product, article or other object at a printing station; providing a primary light source of UV light preferably comprising at least one set of UV-LED arrays of UV-LED chips adjacent the printing head; and partially curing the ink dots by emitting light on the ink dots from the primary light source to set and partially polymerize, coalesce, coagulate and/or gel the ink dots so as to substantially inhibit the growth of the ink dots and prevent, running or smudging of the ink dots. The curing of the ink dots are completed by emitting light on the ink dots from a secondary light source, such as from one or more fluorescent lamps.

1 . A method for printing on an object at a printing station, comprising the steps of: 
 printing ink dots comprising a UV-curable ink on the object with a printer having a printer head, the printer head having a primary light source emitting substantially constant intensity UV light from a primary light source, at a printing station, the primary light source comprising a first plurality of UV LEDs emitting a UV light at a first wavelength and a second plurality of UV LEDs emitting UV light at a second distinct wavelength; and,    setting and partially curing the ink dots by emitting the substantially constant intensity UV light from the primary light source on the ink dots printed on the object for partially polymerizing, coalescing, coagulating or gelling the ink dots to substantially inhibit running, smudging, growing, or bleeding of the ink dots.    
   
   
       2 . The method  claim 1  wherein the primary light source comprises staggered arrays of UV-LED assemblies.  
   
   
       3 . The method of  claim 1  further comprising the step of positioning the primary light source above the ink dots.  
   
   
       4 . The method of  claim 1  wherein the primary light source is a separate element from the printer head, and wherein the primary light source is attached to and in a fixed relationship with the printer head.  
   
   
       5 . The method of  claim 1  wherein the first and second plurality of LEDs are first and second LED arrays, respectively.  
   
   
       6 . The method of  claim 1  further comprising the step of substantially completing the curing of the partially cured ink dots by emitting light on the ink dots from a secondary light source to substantially polymerize, coalesce, gel, or coagulate the ink dots.  
   
   
       7 . The method of  claim 6  further comprising the step of positioning the secondary light source below the ink dots.  
   
   
       8 . The method of  claim 6  wherein the secondary light source comprises at least one fluorescent lamp.  
   
   
       9 . A method for printing and curing ink dots of ultraviolet (UV) curable ink dispensed from a printing head of an ink jet printer or other printer onto an object, comprising the steps of: 
 emitting UV light from a primary UV light source at a substantially constant intensity on ink dots printed on the object for partially curing the ink dots; and,    emitting UV light on the ink dots from a secondary UV light source for completing the curing of the partially cured ink dots,    wherein the step of emitting UV light from the primary UV light source comprising emitting UV light at a plurality of distinct UV wavelengths.    
   
   
       10 . The method of  claim 9  wherein the primary UV light source comprises staggered arrays of UV-LED assemblies.  
   
   
       11 . The method of  claim 9  wherein the secondary UV light source is located adjacent to or downstream of the printer head and above or below the ink dots.  
   
   
       12 . The method of  claim 9  wherein the primary light source is positioned above the ink dots.  
   
   
       13 . The method of  claim 9  including carrying the primary light source in fixed relationship with printer head.  
   
   
       14 . The method of  claim 9  including positioning the secondary light source below the substrate carrying the ink dots.  
   
   
       15 . The method of  claim 9  wherein the secondary light source comprises at least one fluorescent lamp.  
   
   
       16 . The method of  claim 9  further comprising the steps of: 
 moving the primary light source relative to the object being printed as the printing head is printing ink dots on the object for curing the ink.    
   
   
       17 . The method of  claim 9  wherein the step of emitting a substantially constant intensity UV light from the primary UV light source comprises substantially continuously measuring a sensed intensity value representative of the UV light intensity from the primary light source and adjusting the primary UV light source in response to the sensed intensity value for maintaining substantially constant UV light intensity.  
   
   
       18 . The method of  claim 9  wherein the printing head is reciprocated transversely of the object together with the primary UV light source.  
   
   
       19 . A method for printing and curing ink dots of ultraviolet (UV) curable ink dispensed from a printing head of an ink jet printer or other printer onto an object, comprising the steps of: 
 emitting a substantially constant intensity UV light from a primary light source on ink dots printed on the object for partially curing the ink dots, the UV light intensity being maintained substantially constant by measuring an intensity level representative of the UV light intensity of the primary light source and cooling the primary light source as a function of the intensity level to maintain substantially constant UV light intensity, and,    emitting UV light on the ink dots from a secondary UV light source for completing the curing of the partially cured ink dots.    
   
   
       20 . The method of  claim 19  wherein the step of emitting UV light from a primary UV light source comprising emitting UV light of a plurality of distinct wavelengths of UV light.