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.

Description

[0001] This application claims priority benefit of European Patent Application No. 05107997.8 filed Sep. 1, 2005, which is hereby incorporated by reference. BACKGROUND OF THE INVENTION [0002] The present invention pertains to 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 directing radiation toward the substrate. The present invention also pertains to an ink suitable for application in the present method and a printer for applying the method. [0003] Such a method is known from European patent EP 1 349 733, issued Nov. 10, 2004 as well as from U.S. Pat. No. 6,145,979 issued Nov. 14, 2000. Radiation curable inks have become widely considered in recent years as the...

AI Technical Summary

Benefits of technology

[0004] It is an object of the present invention to overcome or at least mitigate the above described problems. To this end, a printing method has been devised, wherein control 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. The present invention relies on the use of an agent that is able to gel the carrier composition of the radiation curable ink. Gelling the carrier composition in fact means that the agent thickens the carrier composition by forming a three-dimensional structure therein. The carrier composition is then considered as being a gel. It appears that by gelling the carrier composition of the ink, the interaction with the substrate is dominated by the spreading behavior of the ink as such. In other words, the type of substrate appears to be only of very minor importance for the ultimately acquired dot gain. Surprisingly it further appears that the type of ink (actually the type of carrier composition) is also of minor importance in the spreading behavior. We have found that once the ink is gelled, it is the gel-structure that, in fact, dominates the spreading behavior. This leads to the very favorable result that ink as well as substrate characteristics no longer dominate the ultimately acquired dot gain. In practice, this means that the dwell time can be chosen practically the same for every type of ink-substrate combination. This greatly simplifies the printing method and corresponding printer.

Problems solved by technology

In general, if the gelling agent forms a second phase in the ink at the operating temperature, this gives rise to unstable and unpredictable processes when printing the ink from an inkjet print head, which typically has multiple miniaturized ink chambers for jetting the ink droplets.

In particular, if the gelling agent consists of insoluble particles, there is a tendency of these particles to coagulate and clogg the print head ink chambers.

This ink is therefore almost unsuitable for inkjet printing.

However, it is not known from this patent that the gelling agent should be soluble in the carrier composition at the operating temperature of the print head, nor that the gelling agent has to be able to reversibly gel the ink in order to be practically suitable for inkjet printing.

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