UV inkjet

Goodrich JE. (2006) New raw materials for high temperature UV inkjet, Sartomer Technical Paper, www.sartomer.com. 

The predominant chemistry for formulating UV curable inks is acrylate-based free radical curing. Most UV inkjet formulations are mixtures of several different acrylates chosen for their individual properties which, when combined with photoinitiators, achieve the required specification. Because of the extremely low viscosity of the... 

One of the means used to modify monomers and polyester acrylates further is to amine modify them. This is normally done using a Michael addition reaction between the acrylate and an amine. The benefits of amine modification are normally seen with increased cure speed since this will tend to overcome the effects of oxygen inhibition in the cure process. Amine oligomers and synergists can also be low viscosity and give improved flexibility to a film. One disadvantage of these materials maybe that perhaps they do not possess the stability required of UV inkjet ink formulations. They are also very prone to yellowing and are unstable with some forms of adhesion promoters. 

Therefore, there are many different types of photoinitiators available for the formulator. Each has specific properties. Some of the more common ones used in UV inkjet formulations are listed here. 

Table 1. UV inkjet markets, 2005 and 2010 ( million) Source Pira International...

The first five chapters of the book focus on fundamental aspects of printing technologies, pigments and ink formulations and, and interactions of the inks with the substrates. The next six chapters focus on actual inkjet inks formulations and raw materials, by discussing the main groups of inks waterborne, solvent-based, and UV inks. The last five chapters present rmique ink systems and functional inks, such as those for obtaining 3D structures or printed electronic devices. 

There are currently four main types of inkjet inks phase-change, solvent-based, water-based, and UV curable. Other types exist, but are less prevalent, such as oil-based and hquid toner (for electrostatic inkjet technology). Hybrid versions of the four main types also exist (e.g., water-based inks containing some amount of solvent). The various inkjet ink types will be discussed briefly in this chapter, and will be followed by detailed description in separate chapters (solvent-based, water-based, and UV cmable inks). 

Noguchi H, Shimomura M. (2001) Aqueous UV-curable ink for inkjet printing. RadTech Report 15(2) 22-25. 

In the final analysis, the separation between the different types of inkjet solvent, UV, is somewhat arbitrary and indeed there are advantages to mixing solvent into radiation curable inks. ... 

Several types of fluids may be jetted via inkjet heads, which can be of the continuous inkjet variety (CIJ, primarily aqueous or solvent-based), thermal inkjet (TIJ, primarily aqueous, but some solvent and UV/aqueous hybrids exist), or piezoelectric drop-on-demand (DOD, aqueous, solvent, oil, UV curable). While there are advantages and disadvantages for each type of hardware and fluid, a clear leader in growth has emerged from the list. UV curable inkjet... 

There are several limitations on the physical properties of UV curable inkjet inks for piezoelectric DOD print heads. The viscosity needs to be fairly low — 8-12 cps at the jetting temperature (most print heads have on-board heaters, capable of reaching up to 70°C in many instances). The surface tension of the inks is also important, and depends on the print head technology being utilized. Some print heads are equipped with a non-wetting faceplate, while others work best with fairly high surface tension fluids (mid 20s to upper 30s, dynes/cm)... 

These requirements make formulating UV curable inkjet inks more challenging than for applications where low viscosity is not mandatory. This chapter hopes to provide an introductory look at formulating UV curable inkjet inks for printing via DOD print heads. 

Most UV curable inkjet formulas are comprised of the following materials ... 

The majority of the monomers and oligomers used in UV curable inkjet ink formulations are acrylates of varying functionalities, although occasionally materials such as unsaturated polyester resins are used as well. Figure 2 shows examples of the acrylate moiety. Acrylates are skin sensitizers and should be handled with caution. 

Table 2 lists only four raw materials, if the photoinitiator package is considered to be one material. However, it will have all the critical properties of a UV curable inkjet ink — low viscosity due to the monomer selection and the abUity to polymerize because of the photoinitiators included. Also, the use of a pentafunctional acrylate will... 

Formulating UV curable inkjet inks for piezoelectric print heads requires technical knowledge as well as creativity to meet the strenuous requirements that the print markets, particularly the industrial printing arena, demand. The basic components found in most inkjet ink formulas include monomers and oligomers, pigments and dyes, photoinitiators, and additives. 

De Rossi U, Bolender O, Domanski B. (2004) Dynamic surface tension of UV-curable inkjet inks. IS T s NIP20 2004 International Conference on Digital Printing Technologies, pp. 788-792. 

This chapter looks at the raw materials available to UV curable inkjet ink formulators. The main emphasis is on the performance trends of the raw materials, thus hopefully enabling formulators to produce inks that fulfill the greater performance demands required as the technology expands. 

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