Inkjet ink

Capillary pressure gradients and Marongoni flow induce flow in porous media comprising glass beads or sand particles [40-42], Wetting and spreading processes are an important consideration in the development of inkjet inks and paper or transparency media [43] see the article by Marmur [44] for analysis of capillary penetration in this context. 

There is a very wide range of prices for products. Consider the examples listed in table 9.5. The listing shows a 10 orders of magnitude difference in price from tap water to diamond. The price per pound of diamond is 10,000 times higher than inkjet ink. 

The ink for inkjet printers is essentially colored water, and the current formulation of ink is about 75% water, plus dye and glue (Kang 1991, Le 1998, Pond 1999). The ink should flow readily from ihe inkwell to the nozzle, and then to the paper, without dripping or clogging. The viscosity of current inkjet ink is from 2 to 8 cP. The droplets formed should be very uniform in size, and should be as small as possible to increase the resolution. When the droplet hits the paper, the droplet should penetrate the fibers without splatter, which would increase the diameter of the dot on the printed text or picture. The surface tension of current ink is around 45 to 50 dynes/cm, which is much lower than water at 70 dynes/cm. It is believed that if the surface tension is raised from 45 to 65 dynes/cm, the spread (or ratio of diameter of spot on paper/diameter of droplet) would decrease from 3.3 to 1.1. Much higher resolutions... 

Observations Image fading occurs with inkjet ink printing systems since these materials... 

Although spin coated OTFTs with PQT-12 semiconductors have high mobility and on/off ratio characteristics, the performance of those fabricated by inkjet patterning is more variable. This may be attributable to the tendency of PQT-12 solution to gel at room temperature, leading to nonuniformity in the jetted semiconductor channel layers. This deficiency of the PQT solution as an inkjet ink is expected to be a practical challenge in manufacture, and must therefore be addressed. By study of the solution behavior of PQTs, we have subsequently developed a nanoparticle dispersion of PQT-12, which effectively resolves this challenging problem (vide infra). 

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. 

In achieving specific printing applications, the whole printing system should be evaluated, namely the print head, the fluid that is jetted from the print head (inkjet ink), and the substrate onto which the ejected droplets are placed. For apphcations, the requirements are estabhshed, defining the type of fluid chemistry, which directs the selection of the hardware and drives the implementation. 

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). 

Therefore, while formulating new inkjet inks, the formulator must take into consideration the effect of each component on the overall performance of the ink, from storage in the ink cartridge, through... 

It should be emphasized that formulation of a new inkjet ink would require the integration of aU three, in addition to issues such as environmental and health regulations. 

For inks which contain pigments, the most common problem is aggregation of the pigment particles due to the inherent instability of most dispersion systems. Since most modern inkjet inks for graphic applications contain dispersed pigments, the stabilization mechanisms of dispersions will be briefly discussed below. 

Conventional water-based and non-aqueous inkjet inks are mixtures of several components, including volatile solvents, dissolved materials, and dispersed solids (for pigment inks). When the ink reaches the nozzles prior to jetting, the volatile components may evaporate from the nozzle. Therefore, the liquid in the vicinity of the nozzle can have a composition which differs from that of the bulk ink which is further back in the print head supply channels. This disparity causes differences in the physicochemical properties of the ink (e.g., an increase in viscosity or decrease in surface tension)... 

Mendel J, Burner D, Bermel AD. (1999) Particle generation and ink particle size effects in pigmented inkjet inks — Part 11. /Nanopar Res 1 421-422. 

Print head technology determines inkjet inks major characteristics, the latter being covered in the chapter "Inkjet inks Requirements". A major characteristic, substantially differing from standard printing inks, is the viscosity. While the viscosity of printing inks vary from several hundred up to several thousand cPs (centi Poise) — the viscosity of inks used for inkjet applications is in the range of a few cPs for the SOHO (Small Office and Home) printers and up to 20 cPs for commercial printers using industrial print heads. 

The various effects of inkjet ink on top of a non-porous substrate are illustrated in Fig. 1. 

Using Porous Substrates — here inkjet ink will penetrate into the pores of the substrate very quickly, causing low optical density at the surface and a potential "strike through" phenomenon when ink penetrates all the way to the other side of the substrate. Formation... 

A thorough review, published by Kodak, describes one of their products — the Ultima Picture Paper which is intended to be used with inkjet inks. This is a general description which very weU demonstrates the use of each of the building blocks we have been reviewing, in a commercial product. The basic structure (cross-section schematic) of the paper is described in Fig. 7. 

Reactive inkjet inks are widely described in the patent literature. Well over 100 patents have already been issued which claim different reactions between an ink component and substrate top-layer to enable high print quality, eliminating all undesired effects which are caused by the non-viscous inkjet ink. A breakdown of... 

This approach wiU not only eliminate intercolor bleeding but might resolve all inkjet ink issues which have been reviewed above. Anionic... 

The oldest method for the modification of carbon black surface chemistry is oxidation. Common oxidants include air, hydrogen peroxide, hypochlorites, nitric acid, nitrogen dioxide, ozone and persulfates. Each reagent produces a mixture of oxygen functional groups on the surface, with the distribution depending on the oxidant. Materials that disperse in water can be produced with sufficient oxidation, and hypochlorites and persulfates have been used to make water dispersible carbon blacks for inkjet inks. 

Shakhnovich AL (2006) Fluoroquinolonoquinolones and inkjet ink compositions comprising the same, W02006102500. 

---