The Evolution and Future of Light-Curing Inks: From Traditional Printing to Advanced Applications in Electronics and 3D Printing
Light-curing inks have been used in almost all printing methods: UV offset inks, UV letterpress inks, UV gravure inks, UV flexo inks, UV screen inks, UV pad printing inks and UV inkjet inks, as well as UV varnishes.In 2008, China was the first country to introduce a mandatory product standard for cigarette packet printing, which restricts the benzene solvent content. In view of the extensive use of UV inks for cigarette packet printing, reactive diluents, oligomers and photoinitiators containing benzene solvents cannot be used as raw materials to produce UV inks.
This prompts raw material manufacturers to develop and produce benzene-free active diluents, oligomers and photoinitiators, to ensure the normal production of benzene-free UV cigarette ink. At the same time also for UV printing ink to food, pharmaceuticals and children’s products packaging printing field into the horn.
Into the 21st century, large-format UV inkjet equipment and UV inkjet ink development success, UV ink and enter the new field of digital imaging materials, digital imaging materials leader.
The rise of 3D printing technology has created new application areas for UV ink. Information industry, the development of imaging technology industry to promote the development of optoelectronics industry, so that the light-curing ink to a new field of application: printed circuit boards with resist ink, solder resist ink, character ink, optical imaging line ink, optical imaging solder resist ink for the vast majority of UV inks; fiber optic coloring inks, optical disk inks, smart card inks are also mostly UV inks; a variety of home appliances, computers and cell phones used for Various home appliances, computers and mobile phones used in the production of keyboards, touch switches are inseparable from the UV ink; a variety of metal signs, nameplate production also requires the use of UV resist ink or photoimageable resist ink.
With the introduction of new light-curing technology, new materials, new processes, light-curing ink development prospects are more optimistic about the UV inkjet ink is not only used for large-format inkjet equipment, is now expanding to offset printing computer direct-to-plate (CTP) production; printed circuit board industry with inkjet printing inkjet resist ink, solder-resistant inks and character inks to achieve the digitalization of the production of printed circuit boards; is currently studying the use of epoxy resin substrates in the production of UV ink. Research in the epoxy resin substrate directly printed conductive ink production line, change the production of printed circuits for the addition of printed circuits, labor-saving, material-saving, time-saving, and environmentally friendly and pollution-free.
UV-LED is a new UV light source, semiconductor light source, with a small size, light weight, high efficiency, long life, good security, low operating costs, etc., especially with a low voltage, less heat, no mercury and no ozone generation, etc., for the energy-saving and environmentally friendly UV light source, is developing UV-LED ink has been applied in the field of inkjet is being promoted and applied to offset printing, screen printing, Flexo printing and other printing methods. UV ink made using a dual curing system, in addition to free radical light curing, but also with cationic light curing, heat curing, wet curing, redox curing, anaerobic curing and other curing methods, in the ink UV irradiation stops, although the end of the free radical light curing, but can continue to carry out the post-curing, to ensure that the ink is completely dry, which is difficult to curing of ink layers such as thick ink layers, black and other dark-colored ink layers, as well as the three-dimensional coating of ink Layer curing is a very effective means of printed circuit board applications of light imaging solder resist ink is double curing ink.
Composite UV offset ink is being developed UV offset ink and soy-based offset ink combined, with UV offset ink fast curing, excellent print quality and soy-based offset ink printing suitability, the advantages of low prices, is a novel environmentally friendly ink.
Bio-based UV ink is also from the environmental point of view, from the sustainable development of green printing considerations, the selection of biodegradable cellulose, chitin and other natural polymers as raw materials and made. Meet the needs of the optoelectronics industry, aerospace, military and defense fields such as special inks, such as conductive ink, thermal ink, radiation ink, wave-absorbing ink, etc., but also the direction of the future development of UV inks.
Water-based UV ink is the 1990s began research and development of an environmentally friendly ink, which has both UV ink production efficiency, energy saving, environmental protection and water-based ink non-toxic, safe, water as a diluent is both safe and economical, but also completely avoid the UV ink with acrylic monomer as a diluent for the odor and skin irritation of the drawbacks, but also easy to clean equipment and containers. In addition, electron beam curing (EB) ink is also the future research and development and promotion of green ink, which uses high-energy electron beams to make the ink in the active diluent and oligomer polymerization and physical crosslinking, do not need photoinitiators, cleaner, more environmentally friendly, and therefore is allowed to be used in the food, pharmaceuticals and children’s products on the packaging printing.
The basic composition of light-curable inks is similar to that of ordinary inks, which are composed of the following four types of substances:
| General Ink | Light curing inks | Catalysts | Photoinitiators |
| Joining compounds | Oligomers | Various additives | Various additives |
| Solvents | Reactive Diluents |
Light-curing ink oligomer equivalent to ordinary ink in the connecting material, are film-forming materials, their performance on the performance of the ink plays a major role in the structure of the oligomer must have a light-curing group, belongs to the light-sensitive resin. Light-curing ink in the active diluent is equivalent to ordinary coatings and inks in the solvent, but it is in addition to the dilution effect, regulating the viscosity of the system, and does not volatilize, to participate in the light-curing reaction, affecting the speed of light-curing ink and ink layer of the physical and mechanical properties of the structure it must have light-curing groups of organic compounds. Photoinitiator is equivalent to ordinary ink catalyst, ordinary ink due to different curing methods (such as oxidation, heat curing, wet curing, etc.), the catalysts used are different, such as catalysts, curing agents, etc., and light-curing ink through the absorption of ultraviolet rays by the photoinitiator to produce free radicals or cations, triggering the polymerization of oligomers and reactive diluents and physical crosslinking reaction, the formation of a mesh structure of the ink layer. These two types of ink additives are largely the same, are pigments, fillers, a variety of additives, only light-curing ink additives used to minimize the absorption of ultraviolet light, so as not to affect the light-curing reaction. At the same time, a certain amount of light-curing ink must be added to the polymerization inhibitor to ensure the production, storage, transportation and use of light-curing ink stability.