UV ink is abbreviation of printing ink such as gravure, flexo, lithography, screen printing, etc. that is cured by ultraviolet light. In the past 30 years, people have been working hard, improving, and trying to use it as a new edge discipline in green packaging printing inks, due to their small pollution and quick drying. Less energy consumption has become a new international fashion. "It's also a fresh air and a clean and pleasant land" has long been a common voice of people in the packaging and printing industry. But really high-speed, full-automated, photo-realistic offset printing, especially UV inks on non-absorbing non-polar materials are rare.
The reasons are: the cost is too high, the adhesion is poor, the low temperature does not flow (usually by heating), the film formation process, and even after the film formation photon may be decomposed (free radicals) and so on and is limited by the scope of application. Followed by the film crisp, in the PVC electrostatic film on the screen easily lost or friction off the toner has become a major difficulty, by UV polishing oil workers to make up for their deficiencies are often wasted time and affect the increase in the authentic rate. Therefore, whether UV light curing on non-absorbing electrostatic film materials can achieve technological breakthrough has been affecting the development of this product.
UV-curable inks, abbreviated as UV inks, may be used, which consist of photopolymerizable oligomers and diluting monomers (resin binders), and then added with photoinitiators, colorants, and the like. The linking materials can be roughly divided into three types:
·Reactive group polymerization type;
· Reactive group addition polymerization type of polyallylthiol curing system;
·Ionic polymerization type of epoxy resin.
In order to improve the packaging and printing environment, the equipment and facilities for photo-curing ink, photo-curing varnish are between 15KM and 64KM.
In order to ensure the balance between printing speed and drying speed, people always arrange printing color sequence according to different pigment wavelengths in the color ink system: white ink - black ink - cyan ink - yellow ink - red ink, and according to the color hue To install or turn on the UV lamp (bubble) and adjust the light receiving distance, in order to ensure the high quality of the product and prevent the ink film from falling off, the printers are finally solving the problem by offset printing a UV coating.
Looking at the UV ink and UV coating on the market, the principle of drying is nothing more than photochemical reaction. The first condition is that the molecule must have enough energy photons to become excited (state) molecules. Just as every photon known to people can only activate one molecule; the same molecule can only absorb one photon at the same instant. Therefore, the theory is often interpreted as follows: After a molecule absorbs a photon, an electronic transition to a higher-order energy occurs, and the molecule undergoing an electronic transition is called an excited state (ie, a molecule). This excited state molecule not only releases energy but also releases energy. Returning to the ground state, it is also possible to transfer energy to other molecules or generate free radicals and then transfer the photosensitive polymer to polymerization or photocrosslinking and photobridges.
Whether or not the ink system contains a photoinitiator, its purpose is to cause a photocuring reaction of the UV ink system, which is the result of a photochemical reaction; a UV ink that does not contain an initiator and a UV coating whose photocuring is based on a solvent The result of the chemical reaction of the photopolymerization stage after its system is cross-linked into a network structure. The system contains UV absorbers. In absorbing natural sunlight and fluorescent sources, UV light can be converted into hardened crosslinked ink film structures.
After rigorous categorization and screening of UV inks of the same application, the iodine lamp as a black light source and heat source of a cold light source is considered as a recording test for the ink drying process, and the former is superior to the latter in terms of safety. Because when the UV non-absorbing offset printing ink in the printing ink film material, subject to ultraviolet or visible light irradiation, the outer layer of its electrons are excited to jump to a higher energy level, light absorption can occur.
After applying different adjuvants and using the same colorant to test the unsaturation of Wuhan resin, Xi'an resin and commercially available 191, 196 resins, the test compares different molecules in one molecule, including different unsaturated groups. Qualitative and quantitative analysis of organic compounds and metal complexes of bonds, aromatic rings, and heteroelements. Although the ultraviolet region is 200-400 nm, and the visible region is between 400-800 nm, it only accounts for 4% of visible light. This 4% action produces a photochemical reaction.
Since absorption of light of different intensities tends to occur at different wavelengths, the formed absorption spectrum has a high sensitivity (photochemical reaction) degree, and it can be rapidly dried in the case of invisible curing, and can be designed into a complete set. Fully automated (from offset to curing), also able to adapt to trace, trace analysis and dynamics studies - from light source to light intensity (voltage level not the same), from lamp type to output spacing The same); from the ink film thickness, including the amount of photosensitizer in the system) to the length of the ink pigment wavelength (the more transparent and thinner ink film, the shorter the wavelength; light energy, faster drying); from the substrate surface tension, Hydrogen bonding force, free energy to test its adhesion and so on.