Lnk

Pearlescent pigments not only produce pearlescent effects in printing inks while maintaining the original color tone, but also can bring a variety of metallic luster effects and iridescent luster effects. Therefore, pearlescent pigments are widely used in the printing industry, often used in the printing of various packaging papers, magazines, posters, textiles and other items.

     As far as pearlescent pigments and traditional pigments are concerned, there is a big difference between the two in terms of chemical composition and structure, as follows:

(1) The particle size of pearlescent pigments is relatively large. Taking offset printing as an example, the particle size of ordinary pigments is generally 0.02 to 0.08 microns, carbon black is 0.2 to 0.7 microns, and the size of pearlescent pigments used for printing is 5 to 25 microns, which is much higher than the former. Larger granularity will bring certain difficulties to printing transfer.

(2) The pearlescent pigment is a flake-like structure, which is determined by the shape of the mica core and is also the basis for expressing the pearlescent effect. But it brings inconvenience to printing transfer. In the preparation of inks, high-speed, high-shearing or excessive rolling operations cannot be used, otherwise the pearlescent pigments will be destroyed. Pearlescent pigments, color changing pigments, fluorescent pigments

(3) The microscopic surface of the pearlescent pigment is composed of many grooves, which makes it have a relatively high surface energy.

       In order to avoid the above-mentioned characteristics causing troubles in actual printing, engineers have summarized some practical and effective experience based on years of research for printing inks and printing manufacturers to adopt:

1. Pre-wetting of the pearlescent pigment: Before mixing the pearlescent pigment into the ink, the pearlescent pigment should be wetted. The solvent used for wetting should be compatible with the ink system. Good wetting can make the pearlescent pigment evenly dispersed in the ink, which is the basis for obtaining high-quality pearlescent printing effects. Wetting can also overcome the "dusting" phenomenon of dry powder during dispersion. Pearlescent pigments, color changing pigments, fluorescent pigments

2. The dispersion of pigments in inks: Pearlescent pigments have good dispersibility. In low viscosity inks, low-speed stirring is generally sufficient. Try to avoid the use of three-roller, high-speed mixer or ball/bead mills. The pigment is broken and loses its luster. It is recommended to mix the pigment in the final stage of ink production. When using a disperser or high-speed mixer, the mixing time of each batch should be kept constant and shortest.

 3. Choose ink medium with good transparency: Whether it is ink pigment or linking material, transparency is an important factor that affects the pearlescent luster of the ink.

 4. The distribution characteristics of the pigment determine the effect: the more pearlescent pigments are distributed in the printed coating and the better the uniformity, the better the pearlescent effect will be; another point is also very important: only when the pigment chips are aligned parallel to the surface of the substrate To get the ideal pearlescent effect