Theoretically, it can be rigorously calculated how many photons of the uv-cured material can be cured per unit volume, and the photochemical reaction rate does not take much time. However, the addition of a polymerization inhibitor to the uv oil or ink delays the polymerization time (ie, the curing time) after the photochemical reaction has a direct relationship with the photoinitiator and the polymerization inhibitor.
General uv light oil or ink formulations will be selected within the curing time 0.1 ~ 0.2s. However, the specific time after the formula is determined depends on the following factors:
1 coating thickness
The surface of the coating cures quickly, but the surface layer cures and absorbs ultraviolet light strongly. The intensity of the ultraviolet radiation decays exponentially, lowering the curing speed. Therefore, the coating is cured quickly and slowly.
2 UV intensity
When the intensity is high, the curing time is short, and vice versa.
3 Add solvent
Adding thinners to uv light oils, such as ethanol, slows the curing process.
4 Ambient temperature
Coating temperature of 50 °C ~ 70 °C is the ideal ambient temperature. The uv mercury lamp contains a large amount of visible and infrared components, providing the coating surface with ambient temperature. Therefore, designing the curing machine is not as good as the surface temperature of the material.
5 Oxygen less cure faster
Oxygen has a strong absorption of ultraviolet rays, and nitrogen filling the coating surface will accelerate the curing speed.
The selection of the specific curing time is related to the following aspects:
According to the characteristics of the coating machine, such as screen printing machine, the printing speed is about 600 to 2000 pieces/hour, and the uv gloss oil is coated with a 350 mesh screen, and the power density of 80W/cm lamp can meet the requirement. Four-color offset press printing uv offset printing ink, with three power density 80w/cm lamp, printing speed of 7000 / h. Flexo printing machine, gravure printing machine coating uv light oil, the number of lines is 165 lines anilox roller, with a 120w/cm lamp tube, curing speed of 80w/min. Generally choose to cure faster than the coating speed.
According to the print material temperature resistance. The non-temperature resistant material has a faster curing speed so as to avoid deformation of the material, such as a plastic film, and the coating is cured just after the surface is exposed to light, but the temperature does not reach below and the light is left, so that the material base layer is not deformed. White paper is easy to dehydrate, and it also needs to be cured quickly.
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