The hottest ink color and UV curing

Ink color and UV curing (Part 1)

UV ink has been developed as early as the 1940s, but it has not been developed until the last 20 years, and the industry has a closer understanding of UV ink. However, due to the high price of UV ink, large investment in drying equipment, and more complex use process than conventional ink, all these hinder its wider application

the trend of modern printing towards fast, multi-color one-time printing also puts forward new requirements for inks. Therefore, the advantages of UV inks are more significant. For example, UV ink does not dry on the printing machine, but can dry quickly when printed on the printed matter, which not only meets the requirements of continuous printing, but also meets the requirements of high-speed printing. Requirements for multicolor printing machines

influence of pigments on curing

in order to meet the needs of high-end printing, it is far from enough to rely on three primary color inks. Spot color inks need to be used, but for UV inks, some pigment particles will "compete" with photoinitiators or photosensitizers for the incident UV radiation energy, thus affecting the latter's absorption of radiation energy, so that the beam of the UV electron universal testing machine irradiated on the surface of UV inks is often stuck. Do you know why? Now follow the footsteps of technicians. Let's get to know each other! I hope it can help you that the external light cannot be transmitted directly, but can only bypass the pigment particles above to reach the bottom of the ink layer through multiple reflections and light scattering, which slows down the drying speed and reduces the drying efficiency

UV ink contains thousands of pigment particles that can be repeatedly steam sterilized and still maintain their original mechanical properties. Therefore, UV light must have sufficient intensity to reach the bottom of the ink layer. If the light intensity is insufficient, the bottom of the ink layer cannot be irradiated by ultraviolet light. The ink cannot be completely cured, resulting in the hard outside and soft inside of the ink layer. Due to the volume shrinkage during polymerization, the surface is wrinkled, affecting the printing quality. At the same time, it should be noted that the curing of UV ink is different from that of UV varnish, as shown in Figure 1 and Figure 2. Pigments not only affect the curing of UV ink, but also affect the viscosity, fluidity and wettability of the ink layer. Levelness, etc; The interaction between pigments and reactive substrates will also lead to problems such as the decline of ink storage life or color changes

pigment color and curing

when some yellow pigments are used in the initiating system after the light test composed of acrylate and amine, the ink color will change greatly. The pigments that are difficult to cure are black, white, phthalocyanine and yellow pigments. White and black show two extreme phenomena, white completely reflects light, and black completely does not reflect light to complete the sealing effect in this case

people even think that it seems impossible to cure UV light through a film with a certain thickness and opaque to the light, but optimizing the curing conditions will make it possible to cure UV ink containing pigments well. Some problems can be solved or improved by selecting photoinitiators and pigments according to the absorption characteristics of pigments to UV light, You can also adjust the UV light source to reduce the impact caused by curing pigments