Print Drying
Solidification of specialized ink and coating layers between printing units occurs on multi-color presses to prevent wet-on-wet smearing. This rapid drying process, referred to as inter-deck uv curing, ensures that each ink layer is dry before the substrate receives the next color. Applying ultraviolet light initiates a rapid polymerization of the photo-reactive binders in the ink.
The process allows high-speed printing on non-porous materials like plastic films and metalized paperboards without the risk of offsetting, leading to sharper image definition and improved color trap.
Machine Configuration
Placement of specialized lamps between individual printing units characterizes this dryer setup. In inter-deck uv curing, mercury vapor lamps or light-emitting diodes are positioned directly after the printing nip. This arrangement allows the press to run at full speed without waiting for solvent evaporation.
The lamps are equipped with reflectors and shutters to focus the light and control exposure during stop-and-start operations.
Sheet Temperature
Management of the thermal load on the paper substrate is a challenge with multiple drying stations. Heavy exposure during inter-deck uv curing can overheat the paperboard, causing it to curl or lose moisture. Modern systems use dichroic reflectors to minimize infrared radiation while delivering maximum ultraviolet energy.
