Method for printing a substrate with radiation curable ink, and an ink suitable for application in the said method

Abstract

A method for printing a substrate with radiation curable ink supported on a substrate which includes the steps of providing an inkjet print head at an operating temperature, jetting droplets of the curable ink from the inkjet print head onto the substrate, controlling the interaction between the ink and the substrate, and then curing the ink received on the substrate by directing radiation toward the substrate, wherein the controlling of the interaction is provided for by applying an ink comprising a carrier composition and an agent that is able to reversibly gel the carrier composition, which agent is soluble in the carrier composition at the operating temperature of the inkjet print head and gels the ink when it is received on the substrate. Also provided is an ink for enabling the use of the method and a printer adapted for applying the method.

1 . A method for printing a substrate with radiation curable ink which comprises 
 providing the substrate on a support,    providing an inkjet print head at an operating temperature,    jetting droplets of the curable ink from the inkjet print head onto the substrate,    controlling the interaction between the ink and the substrate, and then    curing the ink received on the substrate by radiating the substrate,    wherein the said interaction is controlled by applying an ink comprising a carrier composition and an agent that is able to reversibly gel the carrier composition, which agent is soluble in the carrier composition at the operating temperature of the inkjet print head and gels the ink when it is received on the substrate such that the ink droplets sufficiently spread over the substrate to provide an adequate interaction with the substrate.    
   
   
       2 . The method according to  claim 1 , wherein the substrate is provided on the support at a first temperature below the operating temperature.  
   
   
       3 . The method according to  claim 2 , wherein the difference between the first temperature and the operating temperature is at least 30 degrees Celsius.  
   
   
       4 . The method according to  claim 1 , wherein the agent is able to thermally reversibly gel the carrier composition.  
   
   
       5 . The method according to  claim 4 , wherein the thermally reversible gelling action is based on physical interaction between molecules of the gelling agent.  
   
   
       6 . The method according to  claim 5 , wherein the molecules form a crystalline network in the carrier composition when the gelling action takes place.  
   
   
       7 . The method according to  claim 1 , wherein the gelling agent is radiation curable.  
   
   
       8 . The method according to  claim 1 , wherein the ink received on the substrate is subjected to a physical treatment before it is cured.  
   
   
       9 . The method according to  claim 8 , wherein the physical treatment comprises the transfer of heat and/or the application of pressure.  
   
   
       10 . The method according to  claim 1 , wherein the print head is scanned over the substrate on a scanning carriage, and the ink of a predetermined area of the substrate is not cured until the scanning of the said area of the substrate is completed.  
   
   
       11 . The method according to  claim 10 , wherein the radiation is sent from a source that is mounted separately from the print head.  
   
   
       12 . A radiation curable ink comprising a carrier composition and an agent that is able to thermally reversible gel the carrier composition, said agent being soluble in the carrier composition at a first temperature and gels the carrier composition when it is cooled to a second temperature below the first temperature.  
   
   
       13 . The ink according to  claim 12 , wherein the gelling agent comprises molecules with a weight-average molecular weight of less than 5000, in particular less than 1000, preferably less than 500.  
   
   
       14 . The ink according to  claim 12 , wherein the ink comprises less than 10%, preferably less than 5% by weight of the gelling agent.  
   
   
       15 . The ink according to  claim 12 , wherein the gelling agent is a crystalline compound.  
   
   
       16 . The ink according to  claim 12 , wherein the gelling agent is radiation curable.  
   
   
       17 . The ink according to  claim 12 , wherein an uncured gelled carrier composition de-gels at room temperature.  
   
   
       18 . An inkjet printer adapted to carry out the method according to  claim 1   
   
   
       19 . A carrier composition containing a gelling agent which is soluble in the carrier composition of the operating temperature of ink print heads; has the ability to thermally, reversibly gel the carrier composition and acts to thicken the carrier composition.  
   
   
       20 . A carrier composition containing stearon as a gelling agent, said carrier composition comprising 1,6-hexanediol-ethoxylate-diacrylate, di-trimethylolpropane tetraacrylate and N-vinylcaprolactam.  
   
   
       21 . A radiation curable ink composition which comprises a radiation curable ink containing the carrier composition of  claim 20.