Glowing Colors: Characterization of Printing Inks using DLS and ELS
Quality parameters of printing inks are highly dependent on the composition for each product and vary by manufacturer. The type, source and particle size of pigment is affecting the hue, color saturation and lightness of the printing ink. Further, additives such as buffers, defoamers, wetting agents or thickeners can be added to obtain an ink formulation with the desired properties. The final product should be a stable colloidal solution, which maintains high applicability and color strength over a certain period of time. This application report explains how dynamic and electrophoretic light scattering can be used to monitor and characterize the particle size and stability of ink formulations without foregoing printing performance.
Ink is an intensely colored liquid for use in spring keels, brushes or fountain pens. In addition to manual application during writing, calligraphy and drawing, automated inkjet processes are also of increasing importance. Ink usually consists of a solution or dispersion of colorants in water or other solvents. Printing ink is a special type of ink which is characterized by a very strong color and often contains a binder.
The composition of inks for inkjet printers varies by manufacturer and is generally not published. It is known that printing ink mainly consists of water (50 – 90%) as well as colorants and other additives. Colorants can either be pigments or dyes. Pigments are small solid particles dispersed in a liquid medium and are usually 100 nm up to 2 µm in size. Quality parameters such as hue, color saturation and lightness can vary depending on the type and source of pigment. In general, dyes color more strongly than pigment-based inks. Dyes are dissolved, not dispersed in the medium. They tend to soak into the paper, leaving blurred edges. To avoid this quickdrying solvents and additives are added. Other additives such as buffers, defoamers, wetting agents or thickeners can added to obtain an ink formulation with desired properties. The final product should be a colloidal suspension or solution, which is not only stable, but maintains applicability and color strength over a long enough period of time. The ink’s particle size is adapted to the respective devices and nozzles. They must not dry in the print head, be small enough to pass through the print head nozzle, but should dry quickly on the paper. Therefore, it is important to monitor the particle size of the final product (1) (2). In the present application report we characterize different printing ink samples in terms of their particle size and zeta potential.
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