In recent years, the use of UV-curable inks has increased in both the silk screen industry and the offset printing industry. It is well known that compared with traditional solvent-based inks, UV-curable inks have the advantages of good gloss, strong stereoscopic effect, and no harmful solvent volatilization. Especially in the drying of inks, UV-light-solid inks can be irradiated under ultraviolet light. Instant curing avoids the shortcomings of traditional solvent-based inks, such as long drying cycle and large floor space, which greatly improves work efficiency and quality. After UV light curing ink is printed, it needs to be cured by UV light curing equipment. The main factors affecting the light-solid quality are the wavelength of the UV lamp, the energy, the speed of the conveyor belt, and the UV machine cooling system.
First, UV curing principle, UV lamp and related technical parameters: 1, UV curing principle: adding a photoinitiator (or photosensitizer) to the specially formulated resin, after absorbing high-intensity ultraviolet light in ultraviolet (UV) light curing equipment Thereafter, active radicals are generated to initiate polymerization, crosslinking, and grafting reactions, which convert the resin from a liquid state to a solid state in a matter of seconds. 2. UV curing lamp: The UV equipment light source currently used in industry is mainly a gas discharge lamp (mercury lamp). According to the pressure of the gas in the lamp cavity, it is divided into low pressure, medium pressure, high pressure and ultra high pressure. Industrial high temperature mercury lamps are usually used for industrial solidification. High-pressure mercury lamps can produce characteristic ultraviolet (UV), visible, and infrared (IR) radiation at wavelengths of 310 nm, 365 nm, and 410 nm. The wavelength of 365 nm is the wavelength used for solidification and drying in the world. The title UV lamp refers to a 365 nm high pressure mercury lamp).
Second, the impact of relevant parameters on the curing quality 1, UV machine wavelength: 365nm band spectrum suitable for general light-curing ink (not suitable for ice, wrinkle and other special spectral requirements of the ink). Excessive stray light of UV lamp will affect the light-solid effect. 2. Power of UV machine: The power required for general UV-light solid ink is 80-120w/cm. If the light-solid energy is too high, the ink will be embrittled. The solid energy is too low to achieve the photo-solid effect. 3. Suction device: When the UV lamp emits ultraviolet light, it will also generate a large amount of heat, so that the temperature inside the machine is continuously increased. The light-solid machine is equipped with a suction device above the UV lamp tube, and the curing process is performed through the exhaust pipe. The ozone generated in the room is discharged outside to achieve the purpose of cooling. When the substrate is too thin or the temperature resistance is very low, it is necessary to determine whether it can meet the requirements by photo-solid test. For substrates with high temperature requirements, we can undertake special processing and install quartz glass plates under the tubes to cool down and further filter stray light.