Pearlescent effect in aqueous ink system (below)

For the filler, rheological additives, etc. should also have the same phase requirements. There are circumstances in which pearlescent inks need to be mixed with colorants to express color. Of course, it should be noted that the colorants here should have good transparency.
2. The morphology of the pigment The thickness of the pearlescent pigment is approximately 0.4 μm, and the size of the front surface of the pigment is 2 μm. Therefore, its overall shape is a very thin platelet-like structure. In addition to the transparency of the pigment, this ruthenium structure is another basis for the expression of pearl luster, but from another perspective, it is very sensitive to the shearing action, and the large shearing motion destroys the pearlescent effect. Therefore, in the process of ink production, we require that pearlescent pigments be blended in a gentle manner, and three-roll mills, high-speed dispersers, and other equipment that may damage the pigment morphology should be avoided.
In some cases, pearlescent pigments need to be mixed with other pigments. At this point, the pigment is first dispersed and stirred separately with a high shearing force and shear rate. After that, the pearlescent pigment is slowly added and dispersed at a low speed and gently dispersed in the pigment because the pearl pigment is easy to be used. Scattered, so this can be done very easily.
If pearlescent pigments need to be braked into inks that have already been dispersed, practice has shown that pearlescent pigments are first “pre-moistened” with water so that they can receive the best results. In aqueous printing ink systems, pearlescent pigments are usually added at a concentration of 20% to 30%.
In order to improve the anti-settling ability of pearlescent pigments in aqueous inks, thixotropic thickeners should be used. This additive helps the pigment to be suspended in the emulsified aqueous system.
However, the facts show that different types of thickeners should be selected for the different order of pearlescent pigments in the different ink manufacturing processes. For example, before and after the pearlescent pigment is added to the ink, the PH value of the ink dispersion will change, and it should be adjusted.
In water-based ink systems, pH is a very important factor, but whether it is acidic or alkaline, it will not affect the stability of the pearlescent pigments. Relative to aluminum powder pigments, this is an advantage of pearlescent pigments in water-soluble systems. In addition, a factor influencing the pearlescent effect of printed products is the distribution of pearlescent pigments in the ink layer. If the pearlescent pigment particles can be arranged in the same direction on the surface of the substrate (as shown in FIG. 2 ), the light reflected by the pearlescent pigments is also reflected. Spread in a single direction, you can achieve the best luster, otherwise (as shown in Figure 3) refracted light is diffusely reflected, its effect is greatly reduced. Practice shows that choosing the right type of thixotropic additives can optimize the directional arrangement of pearlescent pigments.
The directionality of the pearlescent pigment arrangement influences the DOI value (image characteristic value), and the DOI value represents the smoothness of the image surface.
4. Application of Pearlescent Pigments in Waterborne Systems In Europe, pearlescent pigments have been used in waterborne systems in the gravure wallpaper industry and are still the most widely used field. Other areas of celebration include the printing of labels, boxes and special decorative papers and gift wraps.
In terms of coating, a common method is an air knife coating method, and other methods include roll coating, curtain coating, and the like. In addition to ordinary silver-white pearlescent pigments, iridescent interference pigments, pearlescent gold pigments and bronze pearlescent pigments can also be used to express special pearlescent effects.
Due to the fact that it is dead and transparent, it is often overprinted/coated on a variety of backgrounds so that it can acquire unique color effects.
Special effects can also be achieved by adding transparent pigments to aqueous pearlescent inks, such as carbon black or different types of transparent organic dyes or pigments. The use of pearlescent inks can exhibit metallic luster. One of the commonly used techniques is the incorporation of a small amount of carbon black into the silvery pearlescent ink. The original transparent pearlescent ink of Song will show the metallic silver color, with the addition of carbon black. With the increase, the silver can gradually turn from soft to strong metal.
Another widely used field for pearlescent pigments is the printing/printing of textiles, especially pearlescent inks for aqueous systems, the main component of which is butadiene or acrylic resins. In the past, pearl ink was once considered to be inappropriate for rotary screen printing of fabrics. Through years of research and development in the industry, especially with the technical cooperation of pigment suppliers, Pearl Light has been able to maturely apply this field.