Dye-based inks

Printing onto Colored Substrates — Many substrates onto which coding is required are not that suitable for printing with the standard black ink or indeed other dye-based inks, as the colors are too dark for the inks to show up. In this case, the inks need to be formulated with opaque colorants and these will usually be either pigments white, yellow, or blue. Sometimes the formulation will contain a mixture of white pigment for opacity and a dye to color the white. 

Materials. A variety of commercial uncoated and coated printing grade papers were selected for this study (see Table I). These papers were evaluated with an. aqueous dye-based ink of surface tension (y) approximately 60 mN.m-1. 

Surfactants play an important role in the success of dye-based ink as well as of pigment-based ink. 

When inks are used which contain pigments as coloring materials, superior images are formed in comparison to dye-based inks (65). However, the images formed with pigment inks have the problem that they are inferior as the coloring materials may be scraped off when images are rubbed, i.e., they have an inferior scratch resistance. 

Inkjet photographic prints, especially those printed with dye-based inks on porous media, are subject to rapid dye fading when exposed to ambient levels of ozone (5). In contrast, the fading rate is much slower when dye-based inks are printed on sweUable media and moreover, when pigment-based inks are used. High concentrations of ozone under controlled conditions have been used for testing in order to establish a standardized test method for accelerated aging. There is a relationship between the concentration of ozone and the time of exposure. 

This standard is based on Arrhenius methodology and calls for measuring changes in print density that occur as a function of temperature at 50% + 3% relative humidity. The objective was to examine the dark keeping properties of inkjet photographic prints as a function of constant absolute humidity at various temperatures. The primary focus is on commercially available dye-based inks printed onto both porous and nonporous photo-quaUty papers (9). 

Also, the nature of the colorant, i.e., whether the ink is a dye-based ink or a pigment-based ink, will affect the quality of the printing. A proper fixation of the colorant on the surface produces a high optical print density, bright tone, a high sharpness, and high wet resistance. The effects of the above-described issues have been reviewed and exemplified in detail (14). 

Inks for continuous ink-jet printers typically comprise dyes dissolved in water or solvent having salts added to make the ink conductive for electrostatic charging. Whenever waterproof printing is required, low boiling solvent inks ate used. For printers that ate used in office environments, water is used as the ink solvent. Using water-based inks, humectants may be added to inhibit drying of ink in the sump and surfactants ate added to wet the printing surface. 

Much research work has been done and continues to be done on the development of new dyes for this outlet. For instance, Avecia have a range of yellow magenta and cyan dyes, based on the ammonium salt principle above, which do show improved wet fastness properties. An alternative approach adopted by workers at Ilford, based on their experience in colour photography, involves the molecular tailoring and formulation of dyes which aggregate and hence have light fasmess properties nearer to pigments (Archiva Inks). 

Prussian blue was the first coordination polymer and has found extensive applications as a dye and ink. It has inspired the related Hoffman clathrates which are also CN bridged coordination polymers. In contrast Werner clathrates are based on discrete coordination complexes as the host but they do display some of the robustness of coordination polymers. 

Generally, ink dyes for ink jet applications and writing, drawing, or marking materials are selected from food, acid, direct, sulfur, and reactive dyes. The choice of dye depends on the application and the ink used, whether it is aqueous, solvent based, or hot melt, and on the printer type continuous ink jet or drop-on-demand, piezo or thermal inkjet. 

Solvent dyes for solvent based ink-jet inks and hot melt ink-jet systems are selected 1 2 chromium or cobalt complex azo (C.I. Solvent Yellow 83 1 [61116-27-6], C.I. Solvent Red 91 [61901-92-6]), anthraquinone (C.I. Solvent Blue 45 [37229-23-5]), or phthalocyanine (C.I. Solvent Blue 44 [61725-69-7]) dyes. 

Fig. 13.31. Examples of magenta ink-jet dyes based on H-acid (left) and gamma acid (right).

Printing inks, utilized in printing and packaging applications, are colored, liquid materials consisting of essentially two components the colorant, an insoluble solid or a dye, and the vehicle, a liquid in which the colorant is suspended or dissolved. Recent years have seen significant progress in water-based inks, but... 

BioBags are DEN certified for restricted use of metals in soy-based inks and dyes. 

Adhesives Organic and inorganic bases Coolants Cleaners colorants (pigments and dyes) Fragrances Inks Paints Plasticisers (e.g., in plastics) Polymers (rubbers and plastics) Sealants Solvents Stabilisers Synthetic fibres Varnishes Biocides Detergents Fertilisers Fuels Foodstuff additives and flavourings to foodstuffs Medicinal products (for humans and animals) Plant protection products Radioactive substances... 

Perceived or Real Health and Safety Issues — There are a number of issues or perceived issues which customers encounter with the original MEK-based inks. The use of MEK has its share of concerns, based upon the smell and perception that it is a harmful material. Indeed, for this reason inks have been formulated with alternative solvents such as ethanol and methanol, as well as previously discussed acetone, and a variety of acetates, such as ethyl acetate. Some of these solvents have unpleasant odour, some more pleasant smell some have a lower toxicity level. That said, methanol is commonly used as a low odor replacement, but could probably be considered a more toxic ingredient Another component which is often replaced is the Solvent Black 29 dye, this dye does contain chromium as the counter ion and the toxicity concerns of having free Chromium 6 ions in an ink can be an issue for some applications or customers. Dyes with alternative counter ions or pigments have been chosen to replace this material. These requirements are often found in the food processing or pharmaceutical application areas, although they can occur with any customer. 

With the flexographic process, water-based inks can be used on paper (original aniline dye process) where adsorption forms part of the drying process. 

Baso . [BASF AG] Dye bases for brightening gravure inks for illustrations. 

Neptun . [BASF BASF AO] Dye bases for prod, of ball pen pastes, typewriter ribbon inks. 

Typtqihor . [BASF BASF AG] Dye base preparations in olon for brightoi-ing of printing inks. 

The most common inkjet inks are water based, containing either dyes (low cost but prone to fading in the images) or dispersed pigments (more expensive but more permanent images). Some commercial/industrial inkjet inks use solvent-based inks containing dispersed pigments. 

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