Refuse to smash! Solve ink curing is not complete
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We all know that UV inks have the advantages of fast curing speed, high printing color density and good stability, as long as they do not touch ultraviolet rays, they will not dry in the ink fountain, have low odor, and are basically free of VOC. Widely used, what are the prerequisites for using UV?
In order to ensure the curing effect of the UV ink, it is generally required that the wavelength of the UV lamp is between 180 and 420 nm, and the power cannot be less than 80 W/cm. The service life of UV lamps is generally 1000 hours, and over-service will not guarantee curing efficiency. When the condition is allowed, rotating the UV lamp tube by 90° is beneficial to the UV rays being completely radiated on the printing ink layer to improve the curing effect. Also ensure that the cooling and ventilation equipment is good in use to ensure that the operating temperature of the UV curing unit is within the allowable range.
It is well known that the viscosity of UV inks is closely related to the ambient temperature. When the temperature is low, the viscosity is low, and when the temperature is high, the viscosity is high. Therefore, the ink should be taken to the workshop for a period of time before use, so that the ink temperature is under normal printing conditions.
The UV ink curing effect should be monitored during the printing process. After the printing product is cooled to room temperature, the adhesion of the ink layer can be tested with 3M-600 tape. After 24 hours of standing, the adhesion of the ink is optimal.
In order to be a prerequisite for the use of UV inks, it is inevitable that some problems will be encountered in actual printing, such as incomplete curing. The following is an analysis of the causes and solutions for incomplete ink curing.
Ink curing is not complete problem description
There is ink on the paper guide roller between the printing units, and it is transferred to the printing material; the back of the printed product is dirty after winding.
Cause analysis and solution
To solve the problem of incomplete UV ink curing, it is necessary to find the cause from the three aspects of curing device, printing operation and ink itself, and then solve the problem.
First check the surface of the UV lamp and the reflector to see if there is any dirt that hinders the UV light from illuminating the printed product. If it is, clean it and develop the habit of regularly cleaning the UV lamp, lampshade and reflector with anhydrous alcohol. At the same time, check the use time of the UV lamp. If it has exceeded the service life, replace it to ensure that the UV lamp has sufficient power; or open several sets of UV lamps to increase the UV radiation energy. If the printing speed is too fast, the UV radiation energy received by the UV ink is insufficient, and the curing time is too short, so that the UV ink is not cured completely, and the printing speed can be solved. If the ink layer is too thick, only the surface layer of the UV ink will be cured and the internal curing will be incomplete. At this time, the anilox roller needs to be replaced, and the amount of ink is appropriately reduced to reduce the thickness of the ink layer.
The above is an external cause of incomplete UV ink curing, and the internal cause is that the UV ink itself has a narrow range of absorption spectrum of UV light and the emission spectrum of the UV lamp. At this time, a suitable photosensitizer can be added to the ink. The addition ratio is 1% to 3%, and the curing efficiency is improved by enlarging the absorption spectrum range of the ink, thereby improving the curing effect.